Thank you all.

I'll grab the components today and see how I go. I assume it's Ok to substitute 4N25 or 4N28 optos, and I'll get some 2N7000 FETs.

Also the cap is just a standard ceramic?

I'll try the simulated one first. Soren, if I don't have any joy with eblc1388's circuit, I'll try yours.

 

I assume it's Ok to substitute 4N25 or 4N28 optos, and I'll get some 2N7000 FETs.

Also the cap is just a standard ceramic?

Yes, those parts will work fine.

There is a subtle reason for using a MOSFET instead of a plain transistor in this application.

 

Thanks eblc1388, that works fine. Now to take that and extend it with an etched board for 6 of them!

Attached 2 photos - one at 0 setting on the phidget and another at about 60%.

Cheers for the help everybody!

 

And attached a candidate PCB (for home etching) for a 6-way driver.

Any comments much appreciated. The thin yellow lines are jumper wires, as I'll be etching single sided. The red and green get etched, the yellow not.

Connectors are a D15 from the Phidget, in 6 AK pairs, a standard PC molex socket and 2 SIL headers for connecting the lamps.

 

Any comments much appreciated.

I hope you haven't made the PCB when you see this.

 

Sorry eb, see what?

If you mean that those pads are unconnected, that's because it wasn't possible on a single layer design to route them directly to the lamps. Hence the skinny yellow jumper lines.

Or did you mean something else? Sorry if I'm being spectacularly dense!

-- james

*edit* oh good god, yes you're right, those pads should be coming off the MOSFET source, not pin 6 on the opto! What a **** I am! Thank you And no, I always sleep on my boards at least once before I etch them, helps with clarity.

 

eb, what do you use for simulation? I bought Livewire (home version) a long time ago in the UK but I get no response from New Wave Concepts on my registration activation so can't run it.

 

eb, what do you use for simulation? I bought Livewire (home version) a long time ago in the UK but I get no response from New Wave Concepts on my registration activation so can't run it.

You should have come to this forum much much sooner.

Many here in this forum use the FREE LTSpice for simulation. It is extremely powerful and does not has any restriction on number of nodes. It also has a dedicated Yahoo Group(requires registration to be member) where there are common & special component models and examples available.

Enter "LTSpice" into Google will give you the link to the Linear Technology website where you can download the software.

 

Quick update: this is built and tested working with a home-etched board. Thank you to everyone who took the time to contribute. Pretty impressed with the results of press-n-peel blue film for the etching.