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I purchased a high wattage CO2 laser and this blog was created to chronicle my progress.
Friday, July 30, 2004
OPTICS: Quote from Laser Mechanisms
Hm, I got in contact with this place which has a lot of optics. They have a very nice catalog specifically designed for G100s.
I contacted them for a price quote, which they sent, and it really has my interest. Another thing that has my attention is their feeback inhibitor, which I have read is essential to an optics chain to prevent problems due reflection back into the laser.
The quote was from Mark, who I talked to on the phone and was very friendly. He was interested in my project and included an educational discount. He sent this mail message:
Owen,
Please see attached quote.
I gave you the "do-it-yourself" pricing discounts and hope it is in the ballpark of what you were needing.
I threw in everything you might need but you probably don't need it all.
Mike Klos
Laser Mechanisms, Inc.
mklos@lasermech.com
(248) 474-9480
----------------------------------------------------------------------
Another message I recieved from their site was:
07/30/04 3:03 PM
Dear Dr. White,
Unfortunately, we do not have a printed price list that I can send you. If you can tell or sketch for us the configuration you have in mind we can quickly generate a quote for the required items. For the time being, here are prices for some of the most-used components.
PLBBA0041 BEAM BENDER $468
PLVAS0022 VERNIER ADJ.SPCR $578
PLGJM0102 GAS JET MANIF. $578 (same for -0105 or -0107)
PLPET0130 10" PATH TUBE $138
PLPET0134 4" PATH TUBE $110
PLADC0001 ADAPTER CLAMP $187
PLCOL0052 COLLIMATOR 1.6X $1,320
Also unfortunately, I am on vacation next week. If you need additional information, please call or e-mail Mike Klos mklos@lasermech.com, or Mike DelBusso mdelbusso@lasermech.com .
Best regards,
Richard B. (Dick) Barber
Sales Engineer, Laser Mechanisms, Inc.
Phone: 248-474-9480
Fax: 248-474-9277
e-mail: rbarber@lasermech.com
I contacted them for a price quote, which they sent, and it really has my interest. Another thing that has my attention is their feeback inhibitor, which I have read is essential to an optics chain to prevent problems due reflection back into the laser.
The quote was from Mark, who I talked to on the phone and was very friendly. He was interested in my project and included an educational discount. He sent this mail message:
Owen,
Please see attached quote.
I gave you the "do-it-yourself" pricing discounts and hope it is in the ballpark of what you were needing.
I threw in everything you might need but you probably don't need it all.
Mike Klos
Laser Mechanisms, Inc.
mklos@lasermech.com
(248) 474-9480
----------------------------------------------------------------------
Another message I recieved from their site was:
07/30/04 3:03 PM
Dear Dr. White,
Unfortunately, we do not have a printed price list that I can send you. If you can tell or sketch for us the configuration you have in mind we can quickly generate a quote for the required items. For the time being, here are prices for some of the most-used components.
PLBBA0041 BEAM BENDER $468
PLVAS0022 VERNIER ADJ.SPCR $578
PLGJM0102 GAS JET MANIF. $578 (same for -0105 or -0107)
PLPET0130 10" PATH TUBE $138
PLPET0134 4" PATH TUBE $110
PLADC0001 ADAPTER CLAMP $187
PLCOL0052 COLLIMATOR 1.6X $1,320
Also unfortunately, I am on vacation next week. If you need additional information, please call or e-mail Mike Klos mklos@lasermech.com, or Mike DelBusso mdelbusso@lasermech.com .
Best regards,
Richard B. (Dick) Barber
Sales Engineer, Laser Mechanisms, Inc.
Phone: 248-474-9480
Fax: 248-474-9277
e-mail: rbarber@lasermech.com
Sunday, July 25, 2004
ELECTRONICS: Oscillator With Programmable Duty Cycle
I had some available bandwidth so I documented the oscillator with digitally controlled duty cycle on my board.
Oscillator
The CD4541BC programmable timer has a 16 stage binary counter, an integrated oscillator that uses an external capacitor and two resistors. The timer is also programmable by setting the digital inputs to divide the oscillator frequency by to 2^8, 2^10, 2^13, 2^16. The CD4541BC ocscillator frequency can be set by an external RC network that's by the following formula freq = 1 / (2.3 * Rtc * Ctc) where Rs = ~ 2Rtc and Rs >= 10,000 ohms. (Although I've had reasonable results with going down to 1k.)
Obviously there is a lot of flexibility to control the frequency of the oscillator. For my application I just needed a fixed frequency which I set using switch S1. Users that want to control the frequency digitally you could control the frequency by putting TTL control lines on ports A and B.
4-Bit Counter
The next portion of the circuit involves a 74191 4-bit binary counter. The 74191 recieves a clock input and triggers each of the four outputs to produce a series of 4-bit words. The 74191 is called an up/down counter which means it is reversable and count up or down after each clock cycle. When the counter is counting up it produces these outputs on the rising edge of each clock cycle.
Notice that the counter rolls over from 1111 to 0000 at the end of the series.
Wiring for the 74191 is really simple. Pin 14 recieves the clock input from the timer and pins 1, 4, 5, 8, 9, 10, 15 are tied to ground. "N.C." stands for not connected. Pin 16 is tied to Vcc.
Magnitude Comparator 7485
Suppose we had a chip that could read the signals at the outputs of the 74191 and tell when it was at a certain clock cycle. This is accomplished with a 7485 4-bit magnitude comparator. This magnitude comparator performs comparisons of two 4 bit words. The two 4-bit words are called A and B here. Note: The documentation for the 74191 is confusing because it calls the complete word "A", which has four bits (A0, A1, A2, A3) , however; in the 74191 each bit of the word was called A, B, C and D. The comparator has outputs which register when word A<B, A=B, or when A>B on pins 7, 6 and 5, respectively.
Complete circuit
What does this allow us to do? Well, if we wanted to count the pulses that are coming from the timer, we could set a word on the B input of the comparator, wait for the clock to cycle the counter up to that word, and watch the output of pins 6 and 7 of the comparator. The wiring for this circuit is as follows:
The simple pulse generator allows you to program its duty cycle.
The user can set the inputs to B0, B1, B2 and B3 as digital inputs to the 7485 magnitude comparator IC3. The timer, IC1, increments the 74193 4-bit counter, IC2. When the output of the counter is equal to or greater than your duty-cycle code, IC4 an OR gate, goes high until the counter, IC2, overflows. The input code to pins B0, B1, B2 and B4 determine duty cycle of the overall circuit. Suppose the desired duty cycle was 50%. The total number of clock cycles you can measure is 16, and half of those cycles is 8. The input code corresponding to clock cycle 8 is B0=1, B1=1, B2=1 and B3=0. At these settings the output's duty cycle will be 50%. For an input at clock cycle 4, the duty cycle is 25%.
Here is a picture of the outputs of timer and PWM at 50% duty cycle:
Note that the output frequency is CLK divided by 16.
Oscillator
The CD4541BC programmable timer has a 16 stage binary counter, an integrated oscillator that uses an external capacitor and two resistors. The timer is also programmable by setting the digital inputs to divide the oscillator frequency by to 2^8, 2^10, 2^13, 2^16. The CD4541BC ocscillator frequency can be set by an external RC network that's by the following formula freq = 1 / (2.3 * Rtc * Ctc) where Rs = ~ 2Rtc and Rs >= 10,000 ohms. (Although I've had reasonable results with going down to 1k.)
Obviously there is a lot of flexibility to control the frequency of the oscillator. For my application I just needed a fixed frequency which I set using switch S1. Users that want to control the frequency digitally you could control the frequency by putting TTL control lines on ports A and B.
4-Bit Counter
The next portion of the circuit involves a 74191 4-bit binary counter. The 74191 recieves a clock input and triggers each of the four outputs to produce a series of 4-bit words. The 74191 is called an up/down counter which means it is reversable and count up or down after each clock cycle. When the counter is counting up it produces these outputs on the rising edge of each clock cycle.
Notice that the counter rolls over from 1111 to 0000 at the end of the series.
Wiring for the 74191 is really simple. Pin 14 recieves the clock input from the timer and pins 1, 4, 5, 8, 9, 10, 15 are tied to ground. "N.C." stands for not connected. Pin 16 is tied to Vcc.
Magnitude Comparator 7485
Suppose we had a chip that could read the signals at the outputs of the 74191 and tell when it was at a certain clock cycle. This is accomplished with a 7485 4-bit magnitude comparator. This magnitude comparator performs comparisons of two 4 bit words. The two 4-bit words are called A and B here. Note: The documentation for the 74191 is confusing because it calls the complete word "A", which has four bits (A0, A1, A2, A3) , however; in the 74191 each bit of the word was called A, B, C and D. The comparator has outputs which register when word A<B, A=B, or when A>B on pins 7, 6 and 5, respectively.
Complete circuit
What does this allow us to do? Well, if we wanted to count the pulses that are coming from the timer, we could set a word on the B input of the comparator, wait for the clock to cycle the counter up to that word, and watch the output of pins 6 and 7 of the comparator. The wiring for this circuit is as follows:
The simple pulse generator allows you to program its duty cycle.
The user can set the inputs to B0, B1, B2 and B3 as digital inputs to the 7485 magnitude comparator IC3. The timer, IC1, increments the 74193 4-bit counter, IC2. When the output of the counter is equal to or greater than your duty-cycle code, IC4 an OR gate, goes high until the counter, IC2, overflows. The input code to pins B0, B1, B2 and B4 determine duty cycle of the overall circuit. Suppose the desired duty cycle was 50%. The total number of clock cycles you can measure is 16, and half of those cycles is 8. The input code corresponding to clock cycle 8 is B0=1, B1=1, B2=1 and B3=0. At these settings the output's duty cycle will be 50%. For an input at clock cycle 4, the duty cycle is 25%.
Here is a picture of the outputs of timer and PWM at 50% duty cycle:
Note that the output frequency is CLK divided by 16.
Monday, July 19, 2004
ELECTRONICS: limit switches
How to keep the servos from banging off the end of the table.
Most CNC devices have limit switches that detect the position of moving parts when they are near the extreme ends of their linear positions. This prevents collisions of things like ballnuts at the ends of the ball screws, and are also used as points of reference for when the software resets the table to go to the "home" position. Some systems use mechanical switches but in my case I chose to use optical interupter switches made by Fairchild. The advantages of optointerupters like the H21LOB are that they create TTL logic and are fairly accurate.
After some testing I came up with this circuit diagram [jpg][pdf] for the interupters. In this circuit you'll note that in order to daisy chain the optointerupters together it was useful to solder a resistor directly to the interupter. The H21LOB wiring was bundled up with lots of heat shrink tubing (also shown here). The circuit diagram also shows the pinouts for each of DIN connectors which eventually will plug into the back of the electronics enclosure.
Although its very difficult to see in the picture, my cnc table came with a nice mounting bracket (note red arrow) which had some old school interupt switches. I pulled off the bracket, removed the switches, and strung in my interupter circuit into the mount (view here and here). Hot glue was used to make all the wiring that was crammed into the rail stay in place.
The pictures look kind of crappy but once the rails were bolted into place everything looked really good. There are two rails, one for each axis, and each rail has three switches: limit+, limit- and home. The table comes equiped with small pieces of sheet metal that project down onto the rails. When the table slides towards the ends of its total possible travel (around 18 inches) the sheet metal tabs travel between the opto-interupters. The state of the opto-interupters changes, the universal stepper controller picks up the change, and EMC throws a complaint.
ELECTRONICS: removed spurious triggering of JAM circuit
Lets hear it for 10 cent components!
I was having trouble with minor bounces in the power flipping the JAM circuit of the board. Basically lots of idiot lights were flipping when the air conditioning turned on. I added a capacitor to the input of the 74LS373 and everything settled down.
Thursday, July 15, 2004
ELECTRONICS: Hazard due to power supply capacitor
I posted this on the cnczone:
Hey people,
if you consider a circuit diagram like the full wave bridge power supply shown on this page:
http://www.plitron.com/pages/technote.htm
when I built this circuit I used a 30,000uF capacitor at 80V.
Okay, so suppose the power supply is turned on, and then switched off. The capacitor gets charged at some lethal amount, and gets connected to a gecko drive. I've been debugging the gecko which has a plug connector. I've been carefully slipping off the connector and discharging across the caps with a pair of plyers.
Well, I dunno, I guess once the whole system is debugged then maybe it wont really matter if the caps are charged up. But there will always be a gazillion joules waiting across the terminals of my power supply. What I'd like to avoid is leaving a lethal dose in those capacitors. Think of it as protection for my cats.
Owen
and recieved this reply from Mariss, the guy who developed gecko drives...
-------------------------------------------------
1) The drives discharge the capacitor within a second of you turning off the AC power.
2) There are 96 Joules stored at 80VDC (J = C * V^2 / 2) but the voltage is too low to do more than tickle a little bit.
Mariss
-------------------------------------------------
Which is silly, if you see the discharge that comes off of the power supply when the drives are not hooked up to the system. They'd stop a heart no problem. But he was right in that when the drives are hooked up the capacitors are discharged pretty quicly.
Hey people,
if you consider a circuit diagram like the full wave bridge power supply shown on this page:
http://www.plitron.com/pages/technote.htm
when I built this circuit I used a 30,000uF capacitor at 80V.
Okay, so suppose the power supply is turned on, and then switched off. The capacitor gets charged at some lethal amount, and gets connected to a gecko drive. I've been debugging the gecko which has a plug connector. I've been carefully slipping off the connector and discharging across the caps with a pair of plyers.
Well, I dunno, I guess once the whole system is debugged then maybe it wont really matter if the caps are charged up. But there will always be a gazillion joules waiting across the terminals of my power supply. What I'd like to avoid is leaving a lethal dose in those capacitors. Think of it as protection for my cats.
Owen
and recieved this reply from Mariss, the guy who developed gecko drives...
-------------------------------------------------
1) The drives discharge the capacitor within a second of you turning off the AC power.
2) There are 96 Joules stored at 80VDC (J = C * V^2 / 2) but the voltage is too low to do more than tickle a little bit.
Mariss
-------------------------------------------------
Which is silly, if you see the discharge that comes off of the power supply when the drives are not hooked up to the system. They'd stop a heart no problem. But he was right in that when the drives are hooked up the capacitors are discharged pretty quicly.
Wednesday, July 14, 2004
ELECTRONICS: oh yeah!
I got movement out of the motors!
well, okay, just the x-axis.
There were some problems with the circuit diagram as published previously. I'll post a revision.
well, okay, just the x-axis.
There were some problems with the circuit diagram as published previously. I'll post a revision.
Monday, July 05, 2004
SOFTWARE: another one from Jon
OK, you are running a Universal Stepper Controller with open-loop
drives (that is, no encoders feeding back to the USC board?)
If so, switches 1 through 4 must be OFF, and the rest (5 through
10) should be ON. If you are getting a following error, then you
must have a green LED and are out of e-stop. What is happenning
is that the commanded position is getting ahead of the position
as determined by counting the step pulses coming out of the step
pulse generator.
If your acceleration is too high, this can happen even at low speeds.
If your max velocity is high, then you need a lot of gain (that's the
P term in the PID section), and/or more FF1 (velocity feedforward)
to make the step pulse generator go faster.
What is the steps per inch (I'm assuming you are setting the machine up
in inch units)? And, what max acceleration and max velocity do you
have set in the .ini file? (Note that these are in units of in/sec/sec and
in/SEC, respectively.)
Will it work if you jog at a very slow rate?
Oh yeah, one other thing. You can switch the sign of INPUT_SCALE
to make the axes run in the right direction, but the sign of OUTPUT_
SCALE must always be the opposite of INPUT_SCALE. So, if INPUT_
SCALE is -32000.0, then OUTPUT_SCALE must be +1.0
(the 2nd number on the line is a vestige, and should always be zero)
Jon
drives (that is, no encoders feeding back to the USC board?)
If so, switches 1 through 4 must be OFF, and the rest (5 through
10) should be ON. If you are getting a following error, then you
must have a green LED and are out of e-stop. What is happenning
is that the commanded position is getting ahead of the position
as determined by counting the step pulses coming out of the step
pulse generator.
If your acceleration is too high, this can happen even at low speeds.
If your max velocity is high, then you need a lot of gain (that's the
P term in the PID section), and/or more FF1 (velocity feedforward)
to make the step pulse generator go faster.
What is the steps per inch (I'm assuming you are setting the machine up
in inch units)? And, what max acceleration and max velocity do you
have set in the .ini file? (Note that these are in units of in/sec/sec and
in/SEC, respectively.)
Will it work if you jog at a very slow rate?
Oh yeah, one other thing. You can switch the sign of INPUT_SCALE
to make the axes run in the right direction, but the sign of OUTPUT_
SCALE must always be the opposite of INPUT_SCALE. So, if INPUT_
SCALE is -32000.0, then OUTPUT_SCALE must be +1.0
(the 2nd number on the line is a vestige, and should always be zero)
Jon
SOFTWARE: 5220 out of range error
I was able to make this error go away by opening the *.var file and changing the value for the line marked 5220 from 0.000000 --> 1.000000
SOFTWARE: okay, its hard to tell if its software or electronics
White, Owen wrote:
> Hm,
> I got a new error when the emcio is loading up:
>
> Coordinate system index parameter 5220 out of range.
>
> any ideas?
Oh crap! This isn't caused by anything I'm doing, as far as I know. But, I have a pretty good guess what it is all about. A companion file to EMC, that records some settings for reuse the next time EMC starts up, is named xxx.var where xxx is the same as the file name of the ini file. So, if the ini file is usc.ini, then the var file will be usc.var Look in that file for a line that begins with 5220, and you will almost certainly see either a very large number or possibly a badly formatted one. Replace it with 0.000000 and save the changed file, and it should clear up this problem.
These variables save the offsets between machine home and the various workpiece offsets that are set with G92 and G54, G55 etc. They also save some other stuff generally like that.
Jon
> Hm,
> I got a new error when the emcio is loading up:
>
> Coordinate system index parameter 5220 out of range.
>
> any ideas?
Oh crap! This isn't caused by anything I'm doing, as far as I know. But, I have a pretty good guess what it is all about. A companion file to EMC, that records some settings for reuse the next time EMC starts up, is named xxx.var where xxx is the same as the file name of the ini file. So, if the ini file is usc.ini, then the var file will be usc.var Look in that file for a line that begins with 5220, and you will almost certainly see either a very large number or possibly a badly formatted one. Replace it with 0.000000 and save the changed file, and it should clear up this problem.
These variables save the offsets between machine home and the various workpiece offsets that are set with G92 and G54, G55 etc. They also save some other stuff generally like that.
Jon
Sunday, July 04, 2004
ELECTRONICS: more from Jon
>Are there inputs to the parallel that should be high, are there other
>inputs to your board that have to be dealt with to get emc to jog?
>
Yes, you have to have the right condition on the limit switch settings. As my .ini file is set, it doesn't require any switches or wires to be "OK". But, one might want to make the sense polarity the opposite and wire your limit switches as NC to be more reliable.
Jon
>inputs to your board that have to be dealt with to get emc to jog?
>
Yes, you have to have the right condition on the limit switch settings. As my .ini file is set, it doesn't require any switches or wires to be "OK". But, one might want to make the sense polarity the opposite and wire your limit switches as NC to be more reliable.
Jon
ELECTRONICS: more from Jon
White, Owen wrote:
> "The next 4 switches (5..8) select whether each axis will produce step
> pulses (when closed) or full-step phase signals (when open)."
>
> Question 1: confused about the term open and closed. is this analogous
> to a knife switch, where an open switch would be off?
>
Yes, open = off, closed = on. Some dip switch units say open, some say on. Maybe I should change the documents to reflect the more common switch marking, but I wanted to make the point that the "ON" marked on the switch may not equal the function being "ON".
>
>
> Question 2: I'm using gecko drives with US digital encoders, to I want
> step pulses or full-step phase signals?
You definitely want step and direction signals. The phase signals are for driving a Bridgeport step driver board directly. Even the Gecko stepper driver is a lot better.
>
> "Jumper JP4 can be selected to enable or disable the watchdog timer on
> the board. When enabled, the watchdog will force the board into
> Emergency Stop mode when the rate generator registers have not been
> written to in 20 mS."
>
> JP4 has three posts. One is labeled on, the other is labeled off, and
> the last is unlabeled. The plastic jumper is currently plugged over
> the 'on' post and the 'off' post -- is this currently enabled or disabled?
>
The jumper can be to the ON side or the OFF side, and always is on the middle post. When it is to the ON side, the watchdog timer will shut off the step pulses and the auxilliary I/O (solid state relays) when it is not being updated continuously by the computer.
Jon
> "The next 4 switches (5..8) select whether each axis will produce step
> pulses (when closed) or full-step phase signals (when open)."
>
> Question 1: confused about the term open and closed. is this analogous
> to a knife switch, where an open switch would be off?
>
Yes, open = off, closed = on. Some dip switch units say open, some say on. Maybe I should change the documents to reflect the more common switch marking, but I wanted to make the point that the "ON" marked on the switch may not equal the function being "ON".
>
>
> Question 2: I'm using gecko drives with US digital encoders, to I want
> step pulses or full-step phase signals?
You definitely want step and direction signals. The phase signals are for driving a Bridgeport step driver board directly. Even the Gecko stepper driver is a lot better.
>
> "Jumper JP4 can be selected to enable or disable the watchdog timer on
> the board. When enabled, the watchdog will force the board into
> Emergency Stop mode when the rate generator registers have not been
> written to in 20 mS."
>
> JP4 has three posts. One is labeled on, the other is labeled off, and
> the last is unlabeled. The plastic jumper is currently plugged over
> the 'on' post and the 'off' post -- is this currently enabled or disabled?
>
The jumper can be to the ON side or the OFF side, and always is on the middle post. When it is to the ON side, the watchdog timer will shut off the step pulses and the auxilliary I/O (solid state relays) when it is not being updated continuously by the computer.
Jon
Friday, July 02, 2004
ELECTRONICS: a message from Jon
White, Owen wrote:
>Jon,
>
>The board arrived, looks fine, and I'm going to go about the business
>of building supporting circuitry. I'm looking for a recommendation from
>you about something -- I have four digital outputs from my laser, any
>of which when they go high I want the system to stop. I also have a
>water flow sensor (the water cools the laser), again, if this indicates
>that water isnt flowing I want the system to shut down. Could I roll
>all these inputs, the four laser status indicators and water flow into
>a single input into the e-stop?
>
Yes. The cleanest way is if you can make these signals into normally closed relay contacts. Normal would mean a closed contact for no emergency. You just wire them all in series with the E-stop switch. You might also have a "tally board" with a red light for each signal that is in the emergency state,
so you can tell at a glance which one has the problem.
Otherwise, you can OR these signals together and drive one relay or opto-isolator. Since the source for the E-stop chain is only 5 V, you can't string a bunch of opto-couplers in series.
> In your wiring diagram:
>
>http://www.pico-systems.com/images/univuse1.pdf
>
>You use the term "Emergency Stop Chain", maybe I could consider these
>inputs as part of the chain? I'm thinking that would save how many
>digital inputs on the UCS are used, and I don't have to have the
>software on the computer know the actual state of each input. Any
>thoughts on this? There's a digital input for disable on the laser, if
>the board senses an e-stop, is there a way to have the board set the
>disable state? Another question, how does EMC handle an e-stop?
>
When in the E-stop mode, all digital outputs (the 8 solid state relays) are turned off. This is entirely in hardware, and will happen whether the computer is watching or not. If the watchdog jumper is set to "on", then a failure of the computer to update the rate generators in about 20 mS will also cause an e-stop. The step rate generators are also turned off immediately upon an E-stop.
EMC needs digital inputs 14 and 15 to be wired to external ground, as is shown in "sample wiring diagram" on the USC web page at http://jelinux.pico-systems.com/univstep.html
If digital input 14 is not showing a closed contact, EMC will refuse to come out of E-stop. If digital input 14 is closed, EMC will attempt to clear the E-stop condition. If digital input 15 is also closed, then the E-stop can be cleared, SSR 8 is turned on, and the step rate generators are enabled. The other SSR's can be turned on from software.
Most likely your laser can be controlled from the SSR outputs. You might want to replace the AC-output SSRs with an opto-coupler for this purpose, depending on what sort of signal it takes. Then, M03 and M05 commands could turn the laser on and off.
Jon
>Jon,
>
>The board arrived, looks fine, and I'm going to go about the business
>of building supporting circuitry. I'm looking for a recommendation from
>you about something -- I have four digital outputs from my laser, any
>of which when they go high I want the system to stop. I also have a
>water flow sensor (the water cools the laser), again, if this indicates
>that water isnt flowing I want the system to shut down. Could I roll
>all these inputs, the four laser status indicators and water flow into
>a single input into the e-stop?
>
Yes. The cleanest way is if you can make these signals into normally closed relay contacts. Normal would mean a closed contact for no emergency. You just wire them all in series with the E-stop switch. You might also have a "tally board" with a red light for each signal that is in the emergency state,
so you can tell at a glance which one has the problem.
Otherwise, you can OR these signals together and drive one relay or opto-isolator. Since the source for the E-stop chain is only 5 V, you can't string a bunch of opto-couplers in series.
> In your wiring diagram:
>
>http://www.pico-systems.com/images/univuse1.pdf
>
>You use the term "Emergency Stop Chain", maybe I could consider these
>inputs as part of the chain? I'm thinking that would save how many
>digital inputs on the UCS are used, and I don't have to have the
>software on the computer know the actual state of each input. Any
>thoughts on this? There's a digital input for disable on the laser, if
>the board senses an e-stop, is there a way to have the board set the
>disable state? Another question, how does EMC handle an e-stop?
>
When in the E-stop mode, all digital outputs (the 8 solid state relays) are turned off. This is entirely in hardware, and will happen whether the computer is watching or not. If the watchdog jumper is set to "on", then a failure of the computer to update the rate generators in about 20 mS will also cause an e-stop. The step rate generators are also turned off immediately upon an E-stop.
EMC needs digital inputs 14 and 15 to be wired to external ground, as is shown in "sample wiring diagram" on the USC web page at http://jelinux.pico-systems.com/univstep.html
If digital input 14 is not showing a closed contact, EMC will refuse to come out of E-stop. If digital input 14 is closed, EMC will attempt to clear the E-stop condition. If digital input 15 is also closed, then the E-stop can be cleared, SSR 8 is turned on, and the step rate generators are enabled. The other SSR's can be turned on from software.
Most likely your laser can be controlled from the SSR outputs. You might want to replace the AC-output SSRs with an opto-coupler for this purpose, depending on what sort of signal it takes. Then, M03 and M05 commands could turn the laser on and off.
Jon
ELECTRONICS: a message from Jon
White, Owen wrote:
>Jon,
>
>The board arrived, looks fine, and I'm going to go about the business
>of building supporting circuitry. I'm looking for a recommendation from
>you about something -- I have four digital outputs from my laser, any
>of which when they go high I want the system to stop. I also have a
>water flow sensor (the water cools the laser), again, if this indicates
>that water isnt flowing I want the system to shut down. Could I roll
>all these inputs, the four laser status indicators and water flow into
>a single input into the e-stop?
>
Yes. The cleanest way is if you can make these signals into normally closed relay contacts. Normal would mean a closed contact for no emergency. You just wire them all in series with the E-stop switch. You might also have a "tally board" with a red light for each signal that is in the emergency state,
so you can tell at a glance which one has the problem.
Otherwise, you can OR these signals together and drive one relay or opto-isolator. Since the source for the E-stop chain is only 5 V, you can't string a bunch of opto-couplers in series.
> In your wiring diagram:
>
>http://www.pico-systems.com/images/univuse1.pdf
>
>You use the term "Emergency Stop Chain", maybe I could consider these
>inputs as part of the chain? I'm thinking that would save how many
>digital inputs on the UCS are used, and I don't have to have the
>software on the computer know the actual state of each input. Any
>thoughts on this? There's a digital input for disable on the laser, if
>the board senses an e-stop, is there a way to have the board set the
>disable state? Another question, how does EMC handle an e-stop?
>
When in the E-stop mode, all digital outputs (the 8 solid state relays) are turned off. This is entirely in hardware, and will happen whether the computer is watching or not. If the watchdog jumper is set to "on", then a failure of the computer to update the rate generators in about 20 mS will also cause an e-stop. The step rate generators are also turned off immediately upon an E-stop.
EMC needs digital inputs 14 and 15 to be wired to external ground, as is shown in "sample wiring diagram" on the USC web page at http://jelinux.pico-systems.com/univstep.html
If digital input 14 is not showing a closed contact, EMC will refuse to come out of E-stop. If digital input 14 is closed, EMC will attempt to clear the E-stop condition. If digital input 15 is also closed, then the E-stop can be cleared, SSR 8 is turned on, and the step rate generators are enabled. The other SSR's can be turned on from software.
Most likely your laser can be controlled from the SSR outputs. You might want to replace the AC-output SSRs with an opto-coupler for this purpose, depending on what sort of signal it takes. Then, M03 and M05 commands could turn the laser on and off.
Jon
>Jon,
>
>The board arrived, looks fine, and I'm going to go about the business
>of building supporting circuitry. I'm looking for a recommendation from
>you about something -- I have four digital outputs from my laser, any
>of which when they go high I want the system to stop. I also have a
>water flow sensor (the water cools the laser), again, if this indicates
>that water isnt flowing I want the system to shut down. Could I roll
>all these inputs, the four laser status indicators and water flow into
>a single input into the e-stop?
>
Yes. The cleanest way is if you can make these signals into normally closed relay contacts. Normal would mean a closed contact for no emergency. You just wire them all in series with the E-stop switch. You might also have a "tally board" with a red light for each signal that is in the emergency state,
so you can tell at a glance which one has the problem.
Otherwise, you can OR these signals together and drive one relay or opto-isolator. Since the source for the E-stop chain is only 5 V, you can't string a bunch of opto-couplers in series.
> In your wiring diagram:
>
>http://www.pico-systems.com/images/univuse1.pdf
>
>You use the term "Emergency Stop Chain", maybe I could consider these
>inputs as part of the chain? I'm thinking that would save how many
>digital inputs on the UCS are used, and I don't have to have the
>software on the computer know the actual state of each input. Any
>thoughts on this? There's a digital input for disable on the laser, if
>the board senses an e-stop, is there a way to have the board set the
>disable state? Another question, how does EMC handle an e-stop?
>
When in the E-stop mode, all digital outputs (the 8 solid state relays) are turned off. This is entirely in hardware, and will happen whether the computer is watching or not. If the watchdog jumper is set to "on", then a failure of the computer to update the rate generators in about 20 mS will also cause an e-stop. The step rate generators are also turned off immediately upon an E-stop.
EMC needs digital inputs 14 and 15 to be wired to external ground, as is shown in "sample wiring diagram" on the USC web page at http://jelinux.pico-systems.com/univstep.html
If digital input 14 is not showing a closed contact, EMC will refuse to come out of E-stop. If digital input 14 is closed, EMC will attempt to clear the E-stop condition. If digital input 15 is also closed, then the E-stop can be cleared, SSR 8 is turned on, and the step rate generators are enabled. The other SSR's can be turned on from software.
Most likely your laser can be controlled from the SSR outputs. You might want to replace the AC-output SSRs with an opto-coupler for this purpose, depending on what sort of signal it takes. Then, M03 and M05 commands could turn the laser on and off.
Jon
