Relays

[todd432]

Hi all
I have my new controller about 75% done, but I am stuck on trying to get a 3rd relay wired.
I have the PMDX 126 BOB,K1 and K2 working in Mach (pin 1 & pin 14 port 1)
I would like to add a relay to turn on my cross hair laser edge finder. K1 & K2 will power on router and DC system.
How do you wire /turn on/ control a relay....say from pin 16 port 1 on my bob?

I have mapped Mach to pin 16 , and can make the led come on on the board.
If i hook the laser directly into the board it will work ( on and off) though Mach
I have a 12v dc relay to use....but how do I trip the coil on the relay from the bob.
The laser is only 3 volts 5mw


Todd

[Bob at PMDX]

**OOPS** DISREGARD THIS POST.  See the next post by Steve

The "regular" outputs from the PMDX-126 are not designed to directly drive relay coils.  They *can* drive 5V relays if you connect an external "catch" diode, but they cannot directly control 12V relays.  The best way to have the PMDX-126 control the laser power would be to use a 5V-compatible solid-state relay.  We sell one - the PMDX-SSR25 (http://www.pmdx.com/SSR25), though you can get them from other sources as well.

Bob

[Steve Stallings]

Hi Todd,

The style of relay that you show draws too much coil current to run directly
from the logic level outputs of the PMDX-12, even if it were a 5 volt version,
and I regret to tell you that the SSR-25 that Bob mentioned will not work for
DC loads.

Here is an example of a relay that should work:

http://www.digikey.com/product-detail/en/HE751A0510/HE124-ND/475785

This relay provides an internal diode, but you must wire up the connections
to both the coil and the diode. Connect one end of the coil and the Cathode
end of the diode to the output from the PMDX-126. Connect the other end
of the coil and the Anode of the diode to the PCgnd from the PMDX-126.

This relay has a coil current of only 10 milliAmps which makes it possible
to drive it from the logic level output. It can switch up to 500 milliAmps.
My best guess is that your laser diode needs 100 to 200 milliAmps to
operate.

Steve

[todd432]

Thanks guys

SSR-25 that Bob mentioned will not work for
DC loads.

But will it work for AC loads?
If it dose I can work with that.

I order this 
 El.Co Solid State Relay, DIN Rail Mount with Heatsink, 10A SPST, Zero Cross NO, Output: 24-240VAC, Input: 3-32VDC, with LED   from Factory Mation Item#SC1-30D10240A

I can change the ice cube relay to a 110 AC cube and have the SSR trigger the coil that way. Like a double relay, SSR to Coil...if that's even a good idea? This way I can do either AC or DC

Or find a 3 volt dc wall wart and just use the SSR to power that.

My PSU has a 5 & 12vdc output ( drop the voltage down to 3v ... somehow) I was going to use that to power the laser

Thank for your help and grate products on a level that I sorta understand lol

Oh I love this and have used it too lol

Engineering Hell: Everything's right and nothing works.
Bob's Corollary: If everything's right and nothing works, check your assumptions.

THX Todd

[Steve Stallings]

Todd,

The logic outputs from the PMDX-126 can drive the solid state relay that you listed,
and most similar ones.

If speed is not an issue, you can use this style of SSR to control the coil of another
relay, or to control the AC mains input to a wall wart. Keep in mind that the turn
off delay on a wall wart may be several seconds as the laser bleeds down the filter
cap in the wall wart. If you have an electronics recycle place or similar nearby, you
may get lucky and actually find a 3 volt output wall wart.

Steve

[todd432]

Hi all

Just a quick update

My SSR arrived, I installed it and it worked perfect
I changed out the 12v relay for an AC one and the SSR trips the coil.
The SSR is way over kill for what I have it doing but it works. (I really like the red LED that comes on when its powered)
Down the road I should be all set for any upgrades or changes

THX

Todd