Simple precision constant current LDR controller

Status
Not open for further replies.
The TL431 and BC550 form a precision constant current sink, the maximum current is set by the presets RV1 & RV2.

RV3 is the 'volume control', the value should be chosen to set the input impedance of the attenuator.
 

Attachments

  • LDR ATTENUATOR.png
    LDR ATTENUATOR.png
    40.7 KB · Views: 417
In a word, yes.

I can't comment on performance as I haven't built other peoples designs to compare it to, other than say I prefer it to my Alps and Noble pots.

My volume control stays in pretty much the same position, so the non logarithmic/audio taper function doesn't bother me.

I do recommend multi turn presets and a reasonable quality device for the volume control.

I haven't tried this, but it might be possible to get away with a cheaper pot if a couple of small value caps are added between the presets and either end of the pot to ground for decoupling, reversed biased diodes across the caps will also be needed.

The power supply I use is probably a little over kill, but I had it laying around, it's a series reg/current limit/shunt reg combination based around TL431's & IRF510's, the design is nothing new under the sun.

If you build it, post your results/impressions.
 
No, but I will put one together and try to post it over the weekend - if I get time.

As I said, nothing new, all the modules (series reg/constant current/shunt reg) used in the PSU can be found in the TL431 data sheet.
 
Dr.H

PSU as requested, drawn from memory so may not be totally accurate.

I don't recommend building it as it is very inefficient, a LM317 or 7809 would be more than good enough.

I originally built this PSU for another project, and out of curiosity, as I had the parts in my junk box.
 

Attachments

  • LDR PSU.jpg
    LDR PSU.jpg
    97.4 KB · Views: 229
Status
Not open for further replies.