To Peter (4059),
I went out and bought one of the kits you mention Peter and have
set it up running my DSI II cold finger arrangement as it currently
stands.
You mentioned that it can hold your C.F. at 10 deg C (+/-0.5).
After a bit of benchtesting I found that with my fan/peltier/finger
on a full 12v I can have the pelt run until it reaches a low setpoint
then it kicks out.
It rises a certain amount then kicks back in again. All good so far.
Then I decide on a setpoint...I started with 15 deg C.
Nicely cycles...as it should.
Then I set the hysteresis to about halfway. This gives about a 4 deg
delta.
This hysteresis is setable to from between 3 deg delta to about 10 deg
delta.
I could not get it to keep the finger between a degree of change
What setup allows you to have it cycling with only 0.5deg delta?
Have you got the 12v fan running on the full 12v or is it PWM
controlled?
The only scenario I can imagine where the peltier could hold the
temp so close would be the relay clicking in and out rapidly,
every second or so? You wouldn't want that?
OR....the fan speed lowered so the cooling effect is only just getting it
to 10 C and it stays there purely because of it's relationship to
ambient....you wouldn't want that either? Ambient could change over
the hour.
What I'm getting at is the hysteresis of the circuit only seems to let
you have a minimum delta of about 3 deg C.
Sorry for the questions Peter but I'm finding it difficult to duplicate your
exact delta of 0.5 deg C.
It certainly sounds like an ideal setup.
Steve