Esp project 38 build

[GreenJeep]

Hi, I just put together an esp project 38 which is essentially an audio activated switch that can be used to turn on amps, etc.

Project 38

After putting it together I started by checking voltages before putting the opamp in it's socket but for the life of me I cannot see how 5.1v is ever going to show up on that rail near the top. I saw someone asking about this circuit on the all about circuits forum after they couldn't get it going and in that post the schematic had a resistor instead of a diode at D5 but was apparently an older version of the circuit or something. In that case it made a voltage divider. In this case I just don't get it. Anyone built this or can explain this to me? How is 5.1v being created on that rail near the top? Thanks in advance.

And no it doesn't work because I have a little less than 12v where I should have 5.1...

 

[Chris Daly]

Hi, I just put together an esp project 38 which is essentially an audio activated switch that can be used to turn on amps, etc.

Project 38

After putting it together I started by checking voltages before putting the opamp in it's socket but for the life of me I cannot see how 5.1v is ever going to show up on that rail near the top. I saw someone asking about this circuit on the all about circuits forum after they couldn't get it going and in that post the schematic had a resistor instead of a diode at D5 but was apparently an older version of the circuit or something. In that case it made a voltage divider. In this case I just don't get it. Anyone built this or can explain this to me? How is 5.1v being created on that rail near the top? Thanks in advance.

And no it doesn't work because I have a little less than 12v where I should have 5.1...

Schematic of Project 38 shows a zener diode of 5.1v biased on by R8 a 2k2
check your zener is as the schematic shows with its cathode facing the 2k2
and anode to ground. Its a simple zener regulator at that part of the circuit
delivering 5.1v.

 

[PRR]

> I have a little less than 12v where I should have 5.1...

Then your 5.1V Zener is not a Zener, not installed, or not working.

In a pinch it may work with a 1.5k or 1.6k resistor in place of the Zener, but trip-point may vary with wall voltage.

 

[GreenJeep]

Thanks Chris! My zener was not a zener. This makes a lot more sense now! Guess I should avoid circuit building late at night...