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This is the 3D print bed heat controller I am going to show you how to make.

Step 1: Schematic

I found a good circuit for a 555 PWM controller and modified it.

Here is the part list:

1. 555 Timer you can get from Radio Shack

2. IRF8714 This is a MOSFET so handle it carefully it is static sensitive. Its used in my 3D printer for heating the hot end and also in other boards that have built in controls for heated bed.

3. 50K pot The one I used has a long shaft. I had to compensate for that with the 3d printed housing.

4. 1k resistor 1/4 watt

5. 47 Ohm resistor 1/4 watt

6 Two 1N4148 diodes These I had lying around but you can easily locate them at any online store such as Digikey or Mouser.

7. Two 100n These are 100 nano farads the part will have the numbers 104 which is 10 to the -4th power. (.1 PF)

8. One 470uF electrolytic cap. (I didn't have this one on my circuit as I was testing it out but its necessary for the output to be smoother where the voltage does not ramp up and down.

Step 2: Circuit Board

If I had thought of taking photos I would have during construction. I will be making another more advanced and will take snapshots for that one.

This circuit is crude and is my prototype.

Also this will work for anything 12v as long as there is no feedback or reverse voltage on its output.

Also I mentioned that the 470uF cap was not installed. This was so I can test the circuit. The circuit works and I will be adding the component to do another test again.

Step 3: 3D Printed Case

This I had printed out and already made prior to creating this Instructable.

I will try to create a 3D print instructable later

<p>This heat bed control is now obsolete.</p><p>I am in the process of creating a version that will be controlled by my firmware on the 3d printer itself. I found an article that discussed this and I modified my firmware already. Everything works and I am waiting for the circuit board to come in so I can assemble it. :)</p>
<p>What is the advantage of running it in open loop, is it that your board already has a bed heater, but its being used to drive another extruder?</p><p>How do you measure the temperature? with an IR gun?</p>
<p>My printer has a bed heater similar to that of this one: <a href="http://i01.i.aliimg.com/wsphoto/v0/950243525/High-gulity-Reprap-3d-printer-heated-bed-PCB-1-6MM.jpg" rel="nofollow">http://i01.i.aliimg.com/wsphoto/v0/950243525/High-...</a></p><p>What my 3d printer does not have is a way to control the heat. The controller allows me to use the same technology that is used for my extruder only for my bed. </p><p>The temperature was measured using my DVM with a temperature probe.</p>
<p>I have the same bed. The way to attach the thermistor is to place it near the hole in the center and attach with Kapton tape.</p>
<p>Open Loop is good. How do you arrive at the temperature you need? </p>
<p>In order to arrive at the temp I need I adjust the dial (pot) to a position while measuring the bed with a separate meter. The bed will go from 89 degree F to about 140 degree F.</p>
<p>Thanks for sharing!</p>

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