need help with c/esr meter project

AlbertHall

Joined Jun 4, 2014
11,704
is it built on an exact copy of their PCB with the exact same components?
Check value and polarity of the components on the board.
 

MrSalts

Joined Apr 2, 2020
850
yes, i built exactly as shown on the info given in article, have checked pcb to no avail.
It would be interesting to see the project but, I ain't gunna click on any link to a Russian website. Post the photos or screenshots if you want support. If you don't, I'll assume you figured it out yourself.
 

Ian0

Joined Aug 7, 2020
4,146
Have you got exactly the same 7-segment display? I note that it doesn't state whether it is common cathode or common anode.

This isn't the cause of your problem but I can't help wondering if the offset voltage of the LM358 might be a bit of a problem, and the 150pF capacitor on its output might not be such a great idea.
 

Thread Starter

pete g

Joined Jul 27, 2011
12
is it built on an exact copy of their PCB with the exact same components?
Check value and polarity of the components on the board.
Have you got exactly the same 7-segment display? I note that it doesn't state whether it is common cathode or common anode.

This isn't the cause of your problem but I can't help wondering if the offset voltage of the LM358 might be a bit of a problem, and the 150pF capacitor on its output might not be such a great idea.
the readout is common anode. i could not find the one used in the circuit, so had to use a sub. 5461bs-1.
 

dl324

Joined Mar 30, 2015
13,846
i don't think the current resistors are needed in this circuit.
Trust me. It's a poor design.

The circuit is using what appears to be a 3.3V LDO regulator. With no current limiting resistors for a common anode display, each anode driver will be sourcing the maximum current it can provide. The absolute maximum current an output can source is specified as 25mA and devices aren't guaranteed to survive being operated at their absolute maximum parameters.

The display isn't likely to be damaged, but the same can't be said for the microcontroller.

1638728059597.png
 
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