DIY HotPlate

An digital hotplate to rival the $300 version.

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A simple hotplate with digital temperature control for precise control of heating. Initially a simple on and off switch, with a digital set point will be implemented. But profile heating could be added later on. Of the shelf versions of this cost over $200 each. My rough estimate is I can build this design for less than $60 each.

This is a simple hotplate design I am working on to heat up my resin injection molds. For my purpose I only need to heat up to 150F and hold that temperature. So a simple control loop with be used. But I wanted to keep the design open for addition of other features as they are needed. Profile heating and cooling, timers, and external temperature sensing can all be added.

The frame will be laser cut from 0.25" MDF and glued together. Two heater coils will be mounted to a block of aluminum and controller via an arduino uno. The temperature will be displayed on an LCD display.

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  • Circuit Board, Aluminum Plates

    jupdyke01/09/2016 at 00:35 0 comments

    made a little more progress today. I made a small circuit board with a ribbon cable for the LCD screen. Honestly, I am not that happy with this design. If I were to do it again I would order an LCD screen with a serial connection so that it didn't have so many pins to worry about. I looked and they are only a dollar more expensive. But now I have these screens, so I will try to make these work.

    Again i used some hot glue. While the solder holds the wire in place, the wires are thin and it didn't seem very strong. So I added some glue to help. I am not a huge fan of hot glue, but I suppose I am starting to find uses for it.

    The aluminum plates arrived today as well. I need to drill and tap some holes for mounting it. I also might put a corner round on the top just to make it look a little nicer.

  • Steady Progress

    jupdyke01/07/2016 at 01:03 0 comments

    I made a little progress on the hot plates. Mostly just a lot of little things. I soldered some of the wires, added some ring terminals for the relay, changed the wires on the front switch, added a green grounding wire for the aluminum plate and soldered on some header pins so I can plug in to the Arduino.

    I also hot glued the ac / dc converter in place. I am not a big of hot glue actually. I guess I am just used to doing things the industrial way. But since I already gutted the usb charger for this part, I decided to go with it. I hot glued it to the side of the solid state relay because I didn't want to glue it to the case. The relay is screwed in and can be removed fairly easily. This way if I do need to pull it off or change it I can. I is actually sturdier than I thought it would be and still looks fairly clean. Maybe this stuff is not so bad. I also put a few dobs of glue around the wires I soldered on to act as a bend relief. All in all, not bad.

    My aluminum plates are in the mail but wont get here until Jan. 13th and the thermisters wont arrive until Feb 11th. So I looked around the shop for a scrap piece of aluminum I could use to test with. I found this which is a little smaller than I need, but should do the trick to test.

  • We have power

    jupdyke01/05/2016 at 04:11 0 comments

    I got some of the parts mounted into the case and did a little wiring today. Nothing too exciting, but it is all about steady progress. I wired up the LCD screen and tested it out. Here is a picture of it half wired on a bread board.

    The LCD actually requires a fair number of wires to run it. I ordered a few small protoboards to solder up a small circuit board to contain all of this. It needs a couple resistors and a potentiometer and several connections to either ground or 5v. So I can put all of that on the small circuit board and then have a ribbon cable to connect to the arduino. More parts are on their way this week, and hopefully can get it wired up soon.

  • Laser Cut Cases

    jupdyke01/03/2016 at 02:27 0 comments

    I got some laser time and cut out some cases to mount everything into. I used 3/16 hardboard. You can get a 4' x 8' for $13. I used less than 1/4 of of a sheet to make all 3 cases and I was not really trying to conserve material. My store did not sell it in smaller sheets, so I will just have a lot left over. In a full sheet it feels pretty flimsy, but when you cut it into smaller parts and glue them into a 3d shape it is quite strong actually.

    Here is a picture of the parts laying flat

    And here is the dry fitting before gluing together.

    And finally after gluing up, with the electronics in approximate location.

    The next step is to mount things in place with screws and do all the wiring. At that point I should be able to start testing things out. I already have a similar heater working for my first injection mold that I made. If you are interested in some of the details of that project you there are a few posts about it on my other project logs. Here is a link to the first one"

    Tank Chain - Aluminum Mold / Heater

    As always there are a few minor changes I would like to make for future versions of this. The thickness of the board is not really 3/16" so there is a little over hang of the joints. I also think I should have the arduino mounted up on some standoffs, and I might make some of the holes a little smaller so you can screw into the wood. I also want to add some rubber feet so it sits on the table a little better. But nothing is perfect the first go around.

  • More Parts Salvaged / Arrive

    jupdyke12/31/2015 at 22:03 0 comments

    My Arduino Unos arrived along with my rocker switches. Unfortunately my AC power sockets are stuck in the mail until Feb 12th. Odds are they are coming from China and I was not paying attention to that when I ordered them from Amazon. Not a big deal. I remembered that I had a few of these around on some old electronics my work was throwing away. It doesn't happen often but sometimes I actually find useful parts in my junk boxes. I think the trick is you have to acquire enough junk first.

    Here is a picture of most of the parts that will go into the hotplate.

    • Arduino Uno
    • Two Heater Elements
    • Solid State Relay
    • Power Socket with fuse
    • AC / DC Converter
    • LCD Screen
    • Rocker Switch

    Since I plan on building 3 hotplates I have 3 kits. Some of the parts are currently being used in my PID Control Box and I will pull those out after the first two hotplates are working.

    I hope to laser cut the cases this weekend and start mounting everything. Hopefully this project will be one of those easy ones that doesn't stall. But I don't typically have that type of good luck.

  • First Parts Arrive

    jupdyke12/29/2015 at 04:56 0 comments

    I always like when I come home and have packages on my doorstep. Now that my other project for making the tank tracks is starting to grow I can use some of the funds from that to pay for parts for other related projects. The main reason that I need these hot plates is to heat the molds up and cure the resin faster. A decent digital controlled hotplate runs about $200 and I am planning on building three of them.

    The first parts that arrived today were the heater elements, the LCD screens and the USB power converters.

    I am planning on using an Arduino Uno to control the hot plates so I will need to power them. I will have AC power coming in and powering the heaters through a solid state relay. So I needed a way to convert this to 5 vdc. The cheapest and easiest solution was some phone chargers. I got a pack of three for $8.95 just a tad under $3 each. I can't cant think of a cheaper solution than that. I decided to open up the chargers and get access to the circuit board directly. This will make it easier to mount and connect wires to. Here is the tear down photos.

    It would be easy to use use a usb cable to connect the arduino to this. However, I would like to leave the usb open for programming the hotplate after it is built. So I will need to connect directly to the 5 vdc and ground pins instead. I plan to check these on the oscilloscope at work first to make sure the power coming out is not too noisy for that. But i think it will be okay. To make it easier to work with I removed the two short blue wires and replaced it with longer black and white wires of the same gauge. I also removed the usb socket and added a black and red wire to the power and ground pins directly. The last step was to use a little super glue to glue the two halves of the board together.

    For less than $3 I have a nice little AC to 5 VDC power converter which should power the arduino nicely.

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warhawk-avg wrote 11/23/2018 at 15:38 point

You know...with a cheapo [3D printer MOSFET module](, and a [3D printer heat bed]( could heat up close to the 150c~ and maintain it fairly would need to supply an ATX powersupply that could push 12v at at least 10-15A (about 300-400 watts)

Really cool build!!

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greenaum wrote 01/08/2016 at 08:02 point

You probably know this, but those Fotek relays are notorious for being fake. Apparently the real ones have a cut-off corner on the metal name plate. Big Clive took one apart on Youtube, the "25A" relay had a 12A triac doing the switching. 

If you're below 12A, and the relay in question actually has a 12A, you're probably OK, but worth being aware of. Keep an eye on how warm the bottom plate of the relay gets.

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