K8055 PWM for Peltier (TEC) via switching power supply

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1

Hi Guys wonder if you can help,

I have already created a relay card with various configurations of resitors to control the voltage being provided to a Peltier module (using PC power supply and K8055), however I feel this can be acheived more efficiently via the PWM method.

I have looked through lots of the forum posts and am still at a loss whether this is possible with the K8055.

I think the diagram in the following post is the best fit for what I want to do - subtituting the bulb for the Peltier module. http://forum.velleman.eu/viewtopic.php?f=3&t=3412&p=12551&hilit=open+collector+k8055#p12551

The Peltier I am using is - TEC1-12706 running at a maxmum of 12V, around 5A.

Would following the above diagram fry my K8055 board?

Thanks in advance

2

I have made an external PWM, with a TIP120 transistor, allowing me to handle up to 5A

You can find it here viewtopic.php?f=3&t=3899

There are one that can handle up to 10A too

3

Thanks for the speedy response - shame I cant get a transistor tonight :wink:

4

Yep, but you need it, the one on the board can far from handle that load on its own :slight_smile:

5

…will do.

I will probably need to smooth the signal to Peltier module, what type of capacitor would I need and where would it go?

My disclaimer :slight_smile:
I am a newbie and putting together the K8055 was my first ever electronics project.

6

Could I just use the DAC output instead of the PWM for a smoother signal - negating the capacitor?

7

Yes, you can.
Use Darlington transistor to drive the Peltier element.

8

Great.

I have had so much fun with this K8055 board- a brilliant introduction to electronics.

I have created a relay board with various resistors to control the Peltier module, but this is not efficient and the does not look cool, so thought PWM was the route to go.
I’m using the x2 analogue inputs with the K8067 temp sensors and many of the DO are used on for the relays to control fans.

Do you have an example schematic showing a connection via the DAC to a TIP142 and external power source. I’m not sure if I need to worry about the forward bias and thus the diode and resistor?

Thanks for the various suggestions so far :slight_smile:

9

I think something like this should work.

You need big heat sink for the transistor…
The power loss of the resistor will be over 10W too.
If you do not get high enough current you may use lower resistor R1 value.

10

Wow thanks :slight_smile:

What’s the purpose of resistor R1?

11

ahhh, to limit the base currebt from the K8055 :wink:

12

Also you have better control to the collector current by using the emitter resistor R1.
The only drawback is that at max. current (about 5A) there is voltage loss of 2.5V in the resistor. Thus the Peltier element can get only about 9.5V in this case.

You may use lower R1 value to get more “sharp” control to the current.

13

Thanks again - I will post some pics of my progress with this method.