relay to turn plasma on needed with bob campbell

[Wolfesmetalfab]

Is a relay needed with the bob campbell BOB, or can the board control that on its own? I have a cutmaster 51 that has two terminals for connecting for machine use.

see link for pic http://www.cnczone.com/forums/showthread.php?t=48868

I am familiar with that, but need to know if i can just connect those to terminals to the bob, or if I need a relay, and if so, like a regular 12v automotive relay using the 12v out on the board?

any of these work?
12 VDC N.O. RELAY
12 VDC SPDT 30 AMP RELAY
New in Box Solid State Relay SSR 24-480V AC, 25A


Thanks
Brian =)

[bharbour]

The Combo+ BOB has several uncommitted relays on it (3 I think). I have used them on milling machines and used the relays for spindle run/stop, direction and coolant pump control. There is a 4th relay that is controlled by he charge pump on the BOB. If you are not using those relays for anything else in your system, they should be fine. I think the relays are rated at an amp or so and should be fine for a control signal. I can't speak on any of their other models, but the information should be in the docs that are freely downloadable for his boards.

Bob

[Wolfesmetalfab]

what relay should i be looking for if i purchased it separately? I dont need all the extra relays, and $50 I can beat by along ways by just buying the relay I need, but I dont know exactly what to look for.

The bob output voltage is 12v, and the plasma when reading dc volts across the 2 machine switch terminals, it is 11 volts.

I read that i want a solid state relay, and i am not familiar with these. does it need to be, or just a standard relay?

[bharbour]

Originally Posted by Wolfesmetalfab what relay should i be looking for if i purchased it separately? I dont need all the extra relays, and $50 I can beat by along ways by just buying the relay I need, but I dont know exactly what to look for. The bob output voltage is 12v, and the plasma when reading dc volts across the 2 machine switch terminals, it is 11 volts. I read that i want a solid state relay, and i am not familiar with these. does it need to be, or just a standard relay?

I looked at Cambell's "Combo" break out board and it specifies solid state relays for the relay outputs. This means that the relay outputs only have drive for solid state relays which need at most about 30milliAmps to switch on. The first two of your choices in the first post will be way too much load to drive directly.

All of the solid state relays that I have used have an opto-isolated input and the output varies from transistors to triac's depending on whether the relay is designed for DC or AC loads. Solid State Relays need to be selected based on what load you are driving with them.

I looked at the service manual on the Cutmaster 51 and could not find any specifaction on what the torch switch circuit actually drives. It is probably a 12V DC low current control signal, but it might be controlling a relay or have some wierd AC circuit that would not show up on a voltmeter. Without the machine in front of me, I would say spend the extra $50 for the BOB with actual mechanical relays.

Good Luck,
Bob

[Wolfesmetalfab]

I asked Bob Campbell, and he referred the question to james cullins, and james answered

"The THC 300 has a relay for firing the torch. You can use Bob's breakout board and the THC 300 that is all you need. Check out my web page www.soundlogicus.com You can download the manual, install program and other useful files."

I may use the thc300, but want to try it without first to see if I am happy without it.

the cutmaster 51 does measure 10.85 volts across the two torch trigger terminals. It draws .02 amps on activation, when torch is arcing, it switches to -.05 on the multimeter.

Is there a way of testing how much current is ok on the bob ouput for the relay?

I have a relay sitting infront of me, and when tested, it pulls .16 or 160 milliamps. Is this way to much for the BOB output you think? It clicks, so it is not solid state, I am just having a hard time locating a proper solid state relay. In the THC300 manual, it says that when testing, you will hear the relay click, so it is not solid state, why is it ok for them to use, but not me, im confused?

Edit: Something like this may be the ticket...

http://www.mouser.com/Search/Product...BP7tkZuA%3d%3d

The TS3R1G or TS3R2G as shown on the data sheet seem good.

[bharbour]

Originally Posted by Wolfesmetalfab I asked Bob Campbell, and he referred the question to james cullins, and james answered "The THC 300 has a relay for firing the torch. You can use Bob's breakout board and the THC 300 that is all you need. Check out my web page www.soundlogicus.com You can download the manual, install program and other useful files." I may use the thc300, but want to try it without first to see if I am happy without it. the cutmaster 51 does measure 10.85 volts across the two torch trigger terminals. It draws .02 amps on activation, when torch is arcing, it switches to -.05 on the multimeter. Is there a way of testing how much current is ok on the bob ouput for the relay? I have a relay sitting infront of me, and when tested, it pulls .16 or 160 milliamps. Is this way to much for the BOB output you think? It clicks, so it is not solid state, I am just having a hard time locating a proper solid state relay. In the THC300 manual, it says that when testing, you will hear the relay click, so it is not solid state, why is it ok for them to use, but not me, im confused? Edit: Something like this may be the ticket... http://www.mouser.com/Search/Product...BP7tkZuA%3d%3d The TS3R1G or TS3R2G as shown on the data sheet seem good.

You might try asking Mr Cullins how much current can be switched on the relay lines. That would be a non-destructive way to get the drive current capability. It's not impossible that the BOB can drive 160mA into the relay but I would be pretty surprised. The reason that the torch height controller can drive a mechanical relay is that it probably has a transistor that is controlled by the signal from the BOB and is handling the relay current.

If you wind up driving a mechanical relay from the board, you will need a diode across the relay coil to prevent the coil turn-off spike from blowing up the driver on the board (think ignition coil).

The relay TS3R1G or TS3R2G looks like it will work based on your description of the voltage and current on the torch switch. Is there any AC voltage meaured across the contacts? I think that the BOB should be able to drive it as well.

Bob

[Wolfesmetalfab]

There was no AC voltage present, i tested that in the beginning.

If you wind up driving a mechanical relay from the board, you will need a diode across the relay coil to prevent the coil turn-off spike from blowing up the driver on the board (think ignition coil).

Can you explain a little further? I kind of think i understand, but not completely.

Here is the conversation between me and James via email, you may want to read from the bottom up for it to make sense.


The 12v regulator will get very hot. The transformer is rated at 500 ma the optos for limit/home are ran off the same winding of transformer. the rectified voltage is 18v - 12v = 3*.16 =.96 watts so it should be OK
Jim

From: Brian
To: JCullins
Sent: Saturday, January 3, 2009 3:41:30 PM
Subject: Re: Relay for plasma

Ok, if i try the 160ma relay, if it draws too much, will it just not work cause it dont have enough juice, or will it cause damage to the BOB psu?

Brian=)

---- JCullins wrote:
> Brian,
> OK, I think I have a relay board here I can just put 1 relay on it for you.
> and charge accordingly. If you can a 12 volt relay with coin current around 30 milliamps it will do. The contacts need to be 5 or 10 amps. We use 10 amps with the THC.
> Just connect the relay contacts to the 12v and out1 on the breakout board.
> You could try the .16 ( 160ma ) relay as it will be the only one.
> Mount the relay down at the plasma and use twisted wire back to the breakout board.
> Jim
>
>
>
>
> ________________________________
> From: Brian
> To: JCullins
> Sent: Saturday, January 3, 2009 1:32:29 PM
> Subject: Re: Relay for plasma
>
> I may look into the thc 300 in the future, but all i want now, is a relay to turn it on and off, and i want to try running it without and see how it goes. Then after the machine is all done, and i start running alot of parts and find that the THC would be nice to add, when the table is already making me money, then I will add it.
>
> I think this may be the outcome, but for now I am just looking for a relay that will work with the soundlogic board.
>
> I have a mech relay that draws .16 of an amp, is this too much, or will it be ok to use? It should be the only relay that I need, but i dont know how much current is allowed for the output relay connections.
>
> Brian
>
> ---- JCullins wrote:
> > Brian,
> > The THC 300 has a relay for firing the torch. You can use Bob's breakout board and the THC 300 that is all you need. Check out my web page www.soundlogicus.com You can download the manual, install program and other useful files.
> > Thanks
> > Jim

[bharbour]

The voltage regulator heating is not the problem I was expecting from the breakout board, I was expecting that the driver would not sink 160mA, but it sounds like it will.

My comment about the diode is based on the need to protect the driver on the BOB from the inductive kickback that the relay will generate when you switch the coil on and off. If you wire the relay coil as described, with one end tied to +12V and the other end tied to the out1 connection:
Put one diode with the cathode (banded end) to the +12V and the other end to the relay-out1 connection.

For maximum safety, you can put another diode with the cathode on the relay-out1 connection ahd the other end to the ground used by the 12V supply.

The first diode will prevent the switched end from swinging above +12V and the second will prevent it from going below ground. Either can blow the driver, but usually the first diode is enough. I have had good success with ordinary diodes like 1N4004 in the past.

Bob

[Wolfesmetalfab]

cool, he said it does have a diode on the bob for the output, and I think the relay does too, heres a link to the part number http://www.azettler.com/index.php?id...988-1CT-12DC1R

am i correct?

[bharbour]

Originally Posted by Wolfesmetalfab cool, he said it does have a diode on the bob for the output, and I think the relay does too, heres a link to the part number http://www.azettler.com/index.php?id...988-1CT-12DC1R am i correct?

I looked at the relay link you gave and did not see a way to specify the diode on the relay. If there is a diode on the BOB, it is probably sufficient.

Good Luck,
Bob

[Wolfesmetalfab]

Successful cutting! and no sparks or smoke!! (other than the plasma cutter of course!!)

Im far from done, but very happy to see some good progress.

Thanks for the help guys.

If I eventually use the THC300, i will switch to that method of relaying, otherwise, this seems to be working good!

Brian =)

[bharbour]

Congratulations on getting it running!

If you find the voltage regulator that Mr Cullins mentioned running too hot to touch, a heatsink like:
http://search.digikey.com/scripts/Dk...&name=HS116-ND
or
http://search.digikey.com/scripts/Dk...&name=HS114-ND

should help a lot.

Bob