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I'm new in this site And sorry for my english language..

I need a circuit for my little oven.

I use an incandescent bulb (4x100W) for heating, and I want make a dimmer circuit to change output using a temperature sensor (ptc or ntc).

I have an AC Light Dimmer I want to modify. I want to change the potentiometer to ptc but I can't find a 470k ptc...

What are your ideas for it?

enter image description here

Can I use this circuit?

With PIC16F88

Nick Alexeev
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whitebeard_01
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    Show us the schematic diagram of your existing dimmer. – Dave Tweed Mar 04 '16 at 21:10
  • If you do replace the pot with a thermistor, be aware that the thermistor and related wiring is potentially live and dangerous. Is the dimmer potentiometer used as a voltage divider or just as a rheostat? – jms Mar 04 '16 at 21:23
  • How about PWM a solid state relay to turn the bulbs on and off, with the pulse width set by the error signal from your temp sensor, set point. – George Herold Mar 04 '16 at 21:36
  • @DaveTweed I have wall type dimmer I don't have schematic http://i63.tinypic.com/14o29hc.jpg – whitebeard_01 Mar 04 '16 at 21:51
  • @GeorgeHerold Is it problem constantly on-off for incandescent bulbs? I can use basic relay circuit with ntc or ptc... – whitebeard_01 Mar 04 '16 at 21:54
  • @jms Well, thank you for caution.. I think use stepper motor for change value of pot? – whitebeard_01 Mar 04 '16 at 21:55
  • Think I'd recommend high-freq. PWM controlling a power MOSFET to control the output to the bulbs. That way you can use any ptc or ntc thermistor you want; just set your PWM control chip to use a "standard value" thermistor. Using PWM+power MOSFET gives much better efficiency than resistive dimming methods ;) – Robherc KV5ROB Mar 04 '16 at 22:32
  • @RobhercKV5ROB Thank you very much for your advice.. Can you recommend a circuit about this PWM and Mosfet project? meantime I must set max. temperature..

    I find this video https://www.youtube.com/watch?v=PKEJApZ6TFw

     – whitebeard_01 Mar 04 '16 at 22:53
  • The fact that you talk about replacing the potentiometer on the dimmer with a temperature sensor suggests that you want a closed-loop control of temperature. This cannot be done by a simple hack of a dimmer. You'll need to learn a good deal more electronics first. And PWM control of a light bulb is not a great idea, since you would need to isolate the MOSFETs to keep from getting shocked. You might as well stick with the dimmer triacs. – WhatRoughBeast Mar 05 '16 at 00:11
  • @WhatRoughBeast Can I use a PID and SSR for Bulbs? May it problem ? And can you advice PWM circuit for 4x100W bulbs – whitebeard_01 Mar 05 '16 at 00:14
  • Yes you can use a PID and SSR, but it's not simple, and you need to learn a lot more first. And my advice about PWM circuit is to use the triac in a dimmer. Learn about triacs. – WhatRoughBeast Mar 05 '16 at 00:24
  • @WhatRoughBeast Is wiring true for this application?

    http://ecorenovator.org/forum/attachments/tools/2456d1345670408-pid-temperature-controller-wiring-diagram-gif

     – whitebeard_01 Mar 05 '16 at 00:31
  • @WhatRoughBeast Can you advice circuit for PWM and Powered MOSFET? – whitebeard_01 Mar 05 '16 at 00:46

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Here's an example citcuit for using a thermistor & PWM controller (you could hack a dc/dc converter controller to do the job) as a thermostat to run your lights. The xfmr is to drop your AC mains voltage down to whatever supply voltage your MCU needs (a wall-wart would work, as long as your GND isn't isolated).

enter image description here

Robherc KV5ROB
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  • Thank you a lot of dear.. What is value D1, D2, and MCU

    And last thing is how can I set max. temperature..?

     – whitebeard_01 Mar 05 '16 at 01:15
  • D1 & D2 are diodes, any diode rated to the voltage & current will work. As for setting the temperature, that depends on what MCU you choose to use. With some, a variable resistor would work well; for others, can set temperature with software. – Robherc KV5ROB Mar 05 '16 at 01:26