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Digital Current/Voltage Control

kas.lewis

I am looking to control the current/voltage to a device using a microcontroller. The essence of what I am trying to do is control a TEC so that a block of copper/aluminum is kept at an approximately stable temperature. To do this I would like to use a microcontroller running some form of feedback loop that is reading data from a temperature sensor or two and based on that controlling the TEC. I am still looking whether it is the voltage or current that controls the TEC temperature differential but I thought I would get a head start with trying to answer this question which really should not be so hard since I'm sure I have learned this stuff at one point. Anyways thanks for the help in advance.

 

Kas

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  • Hi Kas!

     

    I think John is saying that although you could measure current and try to adjust the voltage so that the current through the peltier can be adjusted, it appears to be linearly related to the voltage anyway. So by varying the voltage, you are varying the current linearly.

    PWM can be considered like an average voltage across the device, so it is a nice way achieving control if it suits your scenario. The reason PWM is often preferred (generally - I have very little knowledge of peltier devices : ( is because it is efficient (little power wasted - if linear control was used, then there would be power loss in the transistor or device used to cause some voltage drop, and that loss could be significant since peltier devices usually pass a fair amount of current - e.g. John's peltier device can take 2A at 6V, which is a lot of power 2x6=12W and then the heat in the transistor would also then need to be taken into consideration). Some control algorithm would still be needed, just that the output of it would control the PWM ratio, not an analog control.

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  • Hi Kas!

     

    I think John is saying that although you could measure current and try to adjust the voltage so that the current through the peltier can be adjusted, it appears to be linearly related to the voltage anyway. So by varying the voltage, you are varying the current linearly.

    PWM can be considered like an average voltage across the device, so it is a nice way achieving control if it suits your scenario. The reason PWM is often preferred (generally - I have very little knowledge of peltier devices : ( is because it is efficient (little power wasted - if linear control was used, then there would be power loss in the transistor or device used to cause some voltage drop, and that loss could be significant since peltier devices usually pass a fair amount of current - e.g. John's peltier device can take 2A at 6V, which is a lot of power 2x6=12W and then the heat in the transistor would also then need to be taken into consideration). Some control algorithm would still be needed, just that the output of it would control the PWM ratio, not an analog control.

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