DIY WB done, may not be working right (probably)

[Scot Sealander]

Jess Gypin wrote:
 
> I have finished the DIY WB using the group board and suggestions. Just fired
> it up on the bench tonight. No smoke. I have measured the output from the
> Vout with a digital multi meter and all I am seeing is 2.49 volts. Heater
> seems to be working as the sensor gets very hot. The heater LED never comes
> on. The output voltage does not seem to change much at all. I was expecting
> about 4 volts free air. Can anyone point me in the right direction? Does the
> LED have to turn on for the measurement circuit to fire up? I wonder if the
> LED is backwards.....Hmmmmmm.

A couple things you need to check.  What voltage is the circuit running
on?  You need a minimum of about 13 volts to get the heater circuit to
go into voltage regulation mode from current limiting mode.  Yes, you
will get 2.5 volts on the output if it stays in current mode.  The LED
does need to be in correctly to get to the sensor part of the circuit to
function.

There may be a lot of questions like this, so it may be a good idea if
we get a list of proper voltages at various parts of the circuitry.

Scot Sealander
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