Hi folks
i want to build an electric oven for home use.i want to use two digital thermostats to regulate the temperature of the oven.In case the primary thermostat develops a fault,the alternative thermostat can maintain the thermostat as i use the oven for yoghurt making.
Yoghurt requires a very accurate ,precise temperature for best results.Does anyone have idea on how i must wire the thermostats?

 

Rather than try to get two thermostats to decide which one is correct, I suggest you have one control the heat and the other control an over-temperature alarm. Then YOU can decide which one is wrong.

 

You can get a PID controller for $20-$50. Wire it up to an accurate temperature sensor (for the temperatures you're interested in, a thermistor is probably the cheapest way to go). You can then build a thyristor proportional control for the AC power to the oven heater if the on/off heating doesn't work well enough (I'm guessing the on/off type of control would work fine for your needs).

 

Sounds good.Someonesdad ,How do i use the thyristor as an interface for switching the heater ON/OFF.Please help.

 

Be sure to build two of them.

 

Be sure to build two of them.

QFT. Dual redundancy is hard to beat.

It is also hard to achieve

 

Whenever there is a reply to my post,i want to be notified via an email .

 

You've got to be kidding. You can buy a yogurt maker for less than $20 new and I see them in thrift stores for almost nothing. I'll humor you and assume you want to make vast quantities in a single container. You only have to maintain 110°F so a big piece of insulated air duct, some light bulbs and a small fan to stir the air should do it. You can use any temperature controller.

There's a slick crock pot controller project in Make magazine.
http://blog.makezine.com/archive/2011/03/how-to-arduino-controlled-yogurt-maker.html

 

Whenever there is a reply to my post,i want to be notified via an email .

Just above your first post in this thread on the menu, click on "Thread tools", then "Subscribe to this thread".
You'll be notified via E-mail anytime there is another reply.

 

I am actually in Africa where those yoghurt kits are no where to be found.

 

I saw your post on the Electro Tech forum under the username "Kwame". If you want some insurance using simple readily available thermostats such as water heater thermostats, you need four of them. Put two in parallel to insure against an underheat by either one and two more in series to insure against overheat. No single thermostat failure can spoil the batch.

 

What? No super high tech PID controller in a place so far off the map that they can't buy a yoghurt machine?