Review my temperature controller project.

[Deeg]

Hello all, I am in the process of finishing up a draft Instructable for creating an automatic temperature controller for a BBQ smoker. Could some of you take a look at the schematic and see if you notice anything that might be wrong? I'd welcome any other input as well.

**broken link removed**

Thanks!

 

[alec_t]

There is no supply decoupling for the IC.
Can a stereo jack handle the current you want to control?
With only 6mA base current the TIP41C collector current may be as low as 90mA.
There are much better transistors than TIP41C (higher gain, lower saturation voltage).

 

[Deeg]

I appreciate you taking time alec_t. I have a couple of follow-ups:

There is no supply decoupling for the IC.

I have no idea what this means. Can you explain please?

Can a stereo jack handle the current you want to control?

How can I figure this out? Is this the kind of thing that would be on a spec sheet for a jack? I've been going with the "it works so it's fine" methodology.

With only 6mA base current the TIP41C collector current may be as low as 90mA.
There are much better transistors than TIP41C (higher gain, lower saturation voltage).

Do you have suggestions? I want to learn this stuff so that I can choose the right transistor in the future. Thanks!

 

[alec_t]

I have no idea what this means.

Then should you be posting circuits on Instructables? Other people may build them and find they don't work as expected.

Can you explain please?

Google 'supply decoupling'.

How can I figure this out?

How much current do you want to switch/control? What is the voltage? AC or DC?

Is this the kind of thing that would be on a spec sheet for a jack?

A reputable manufacturer's datasheet should include voltage and current ratings.

I've been going with the "it works so it's fine" methodology

Ok for your own use; but not if you're publishing circuits for others to use.

Do you have suggestions?

Personally I would use a 'logic level' N-channel MOSFET with a low (<0.1 Ohm) Rds(on) spec and a generous voltage rating to suit the anticipated load.

 

[Deeg]

Thanks alec_t, I appreciate your time. I'll look into the topics you raise.