LM107 OpAmp & LM338 Voltage Regulator

[TinselKoala]

I agree. That's a screwy circuit to use for the stated application, unless there's something you aren't telling us.

Plus to get 20 volts out you'd have to put 21 or 22 volts in, and that's close to or above the rating for the op-amp, as far as I can tell.

If you are looking just for controllable power for illumination using those bulbs, you should look for SCR or Triac or MOSFET based lamp dimmer or motor control circuits. The components are cheap and the circuits are efficient.
Here's a link to one I found. To get more output power you can just duplicate the output stage and parallel it to the pulse generator stage.
http://www.ctshooter.com/dimmer.html
The most expensive component is the box.

[poynt99]

Dave,

That drawing is taken right from the specification sheet, but there is no description of the circuit.

Do you need to vary the output voltage for dimming?

Assuming that circuit works alright, a suitable and available replacement for the LM107 might be the LM318. It is a much faster op-amp, but speed is not required for this application. One small drawback is a 4mV offset voltage, vs. 1.5mV with the LM107. It is good up to +/- 20V though, so only a couple volts less than the LM107. The LM318 is cheap at under $2.

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[Dave_W_Cooksey]

Hi TK the output would be only 12 volts which the lights need
and not 20 volts.

If you guys know of a simple circuit that can handle the lights
please post a drawing of it.

David

[derricka]

Lighting4Art.com sells a 75 watt electronic switching transformer for $19.50 which would power one 55 watt bulb. They also sell a 150 watt transformer which would power two of your bulbs for $63
Input is 120 volts for these transformers.
Hookup is easy, two wires in, two wires out.
(Cannot be used with 120volt dimmers- 12volt dimmers ok)

http://www.lighting4art.com/shop1.asp?group=ETX

http://www.translitesonoma.com/pdfs/Transformers/PS-LVT-0207.pdf

[poynt99]

Dave,

Whether you need dimming or not is an important question before we continue. If not, you're off to the races with something simple. If yes, then that's a slightly different story.

The 150W transformer derricka suggested might be the best solution, however I have not been able to find a diagram for how to hook up a dimmer, nor what to use for it. It does come with a diagram apparently. It's cheaper here....only $40:
http://www.lightology.com/index.cfm/method-light.store_profile/sku-1244XF-LVT1511-ELEAC-ALST/dept-Power%20Supply/szdept_label-

A bit of a diagram here:
http://www.lightsearch.com/Lightech2006/pdf/LVT-151%20AC.pdf

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