Binocular Indirect Ophthalmoscope PUBLIC

Hi MyopiaMedic,

Welcome to the world of electronic circuits, congratulation to your first sketch in CL! I found it very good that you’ve added a description, this is why I reply.

Some hints:

1) When you seek for help / comments you should start a thread in the forums. Publishing a circuit (“public”) makes it available to all, but almost no one will notice that (only the word “ophthalmoscope” made me curious). On the contrary, I try to keep circuits “private” or “unlisted” during design. To me a published circuit should be both, working and have some description how, why and so on (but that’s me …).

2) I’m not an expert, neither in electronics nor in medical devices / application, also I don’t know what you exactly mean by “replicate”, but this is a serious warning:

• Until you are an expert in opto-electronics DO NOT attempt to substitute the incandescent bulb by “modern” devices like a LED.

• Intensity versus wavelength and pulse response (the effect of “dimming”) are COMPLETELY different between LEDs and bulbs.

• Some LEDs may damage the retina without being noticed by a bright light.

*

3) To better understand your circuit (which seems to have some errors as well) you should:

a) Try to find functional groups, such as e.g. “power supply”, “input”, “main” and “output”. These groups often are connected by less than four wires.

b) To avoid confusion it’s good practice to draw “GND” lines at the bottom, supply (+) on top of the diagram

c) In CL you have to add a reference point, usually to the “GND” line, to your schematics (“Essentials”).

d) CL has a fairly functional 555 timer in it’s toolbox.

e) See my example:

4) I don’t know what you finally want to do, why you came to CL, but:

In Circuit Lab (CL) the emphasis is the simulation of circuits, not the simple drawing of schematics.

However, successful simulation requires more than a “working circuit”, I’d suggest you start by CL's examples and read some forum postings. Unfortunately CL has “issues” and very few error messages, don’t get discouraged too quickly.

For the simple drawing the type of diodes is not important. For the simulation it may be, but is not in your case. Just google for the types available in CL (double click the element) and compare them visually to your board.

5) Your circuit doesn’t work, but when I tried to find something what could do what you want (using most of your parts) it seems I faced a glitch (bug?) in CL with the fixed voltage regulator 7805.

I have never used that fixed regulator before but when I try now I face the error message “Solver returned no data”, even in a small test circuit. When adding the (in practice required) input capacitor it works, but I will raise the question in the forums, I think it's not Ok.

However, I added the cap to my sketch and now you can try the Time Domain Simulation:

• Check the current going through the bulb, double click the brightness pot and set K to 0.8 or to 0.2 (0.5 is 50%).

Have fun!

Regards, Sancho