Light sensing using LM324

Thread Starter

Nick100

Joined Dec 21, 2020
10
You can eliminate the 1K resistor Rin and the
1K on the output of the op amp at point B
The max output at point B is likely 3.7 volts not 5.7
Thanks I’ll have a look
I have removed them and just wired through In “ iCircuit” . Yes the voltage is 3.2-3.7.
cheers
 

wayneh

Joined Sep 9, 2010
17,134
I don't see how the first opamp can work on a single supply. Any voltage on the inverting input drives it to the ground rail. The inputs need to be reversed?
 

Audioguru again

Joined Oct 21, 2019
2,959
The photodiode is not working as "photo-conductive" and does not conduct a reverse-biased leakage current. Instead it is "photo-voltaic" and becomes a tiny solar cell and produces a small negative current which causes the opamp output to go positive.

I think your simulation software says "error" because it never learnt anything about a photodiode..
 

Thread Starter

Nick100

Joined Dec 21, 2020
10
The photodiode is not working as "photo-conductive" and does not conduct a reverse-biased leakage current. Instead it is "photo-voltaic" and becomes a tiny solar cell and produces a small negative current which causes the opamp output to go positive.

I think your simulation software says "error" because it never learnt anything about a photodiode..
The photodiode is not working as "photo-conductive" and does not conduct a reverse-biased leakage current. Instead it is "photo-voltaic" and becomes a tiny solar cell and produces a small negative current which causes the opamp output to go positive.

I think your simulation software says "error" because it never learnt anything about a photodiode..
I think you may be right about “ learning about a photodiode “ . I have already asked the developer to include photodiodes and phototransistors and Optocouplers. A significant oversight in my books!
 

wayneh

Joined Sep 9, 2010
17,134
The lm324 can work from 3-32v on a single supply according to Texas Instruments
All supplies are "single supplies": they supply two power rails with a ∆V across them. The difference between opamps its whether they can sense voltages near the power rails.
Dual supply = cannot sense near either rail
Single supply = can sense near one rail (usually the ground rail) but not the other
Rail-to-Rail = can sense near both rails
 
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