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heater bed mod

Forums Hacks and Upgrades heater bed mod

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  • #1161
    phongshaderphongshader
    Participant

    I want to set up the heated bed to be controlled by the Rumba board. I’ve found plenty of info on how to wire this up but I have a question about the physical installation of a thermistor onto the bed or the heater. What glue should I use to attach the thermistor to the heater and where would be, in your opinion, the best location for the thermistor on the heater?

    #1241
    dandan
    Participant

    The little pocket with which the existing thermostat probe is an ideal location. Fill it with Thermal paste and just push the thermistor right in. If your thermistor is too small, encase it in some 2 part high temp epoxy putty. The stuff I typically use is call “Fahrenheit”.

    #1242
    phongshaderphongshader
    Participant

    Now that I think of it, could I use the thermistor that is already installed? If not what thermistor would you recommend?

    #1243
    dandan
    Participant

    Hmm, without knowing the specs of the thermistor – possibly. Use a Multimeter to measure the resistance on the two wires. As a guide, a 100K thermistor should read around 100K Ohm @ 25 deg C from memory. Once you’ve figured the type of thermistor, make sure you select that type in your firmware settings for you heated bed thermistor.

    #1244
    phongshaderphongshader
    Participant

    Starting to modify the heater bed,
    [attachment=1]IMG_0962.JPG[/attachment][attachment=0]IMG_0965.JPG[/attachment]

    #1245
    dandan
    Participant

    Looks cool. Is this to improve efficiency or max temp by insulating the underside? Im guessing you’re on 110v?

    #1246
    phongshaderphongshader
    Participant

    Quote:

    Im guessing you’re on 110v?

    I am indeed.

    I currently have 12v to HB-PWR, HB-OUT to an SSR and the heater bed thermistor plugged into TB.
    [attachment=0]IMG_0895.jpg[/attachment]
    How does this translate to the repeater configuration? Repetier says T1 is usually for heater bed. Also Max PWM value, is that the frequency that the board runs the ssr?
    [attachment=1]Screen Shot 2019-12-18 at 6.30.03 AM.png[/attachment][

    #1247
    dandan
    Participant

    This looks correct to me. The SSR is connected to the 12v heater out . 12v Hester in is connected to 12v which typically runs ancillary power to a 12v heater, in this case it powers the relay and provides PWM. The thermistor connects to heated bed thermistor position, then 110-240v live wire goes through your SSR* (we always recommend getting your work checked by a qualified professional. Wired poorly, this can be dangerous.)

    You’ll likely find more configuration options if you open the configuration.h file. The Rumba Pins are already mapped, so default pins should work fine. To test. Disconnect your AC power and run a MM in diode mode across the AC output. It should give a scratchy beep when the PWM fires up. It will start at max PWM and slow as it reaches and maintains target temperature. Turning everything on, you should fine a new icon for heated bed on your LCD. Before testing the SSR, make sure it’s monitoring properly.

    #1248
    phongshaderphongshader
    Participant

    Quote:

    The thermistor connects to heated bed thermistor position


    Is this T1 or TB?

    #1249
    dandan
    Participant

    TB. If it doesn’t work, try T1 if it’s spare. If not, I’ll need to check the mapping in the pins.h file and send it to you. Feel free to pay with that firmware. It’s pretty hard to do any damage from a configuration.h modofication point of view. Repetier has a myriad of safety features built in, preventing temperature inconsistencies and shutting down the printer when one from any of the thermistors (hotends and heated bed) diverge from the set temperature.

    #1250
    phongshaderphongshader
    Participant

    I need to buy some better quality SSRs! I’ve gone through 2 and I haven’t even run the printer yet. They both lasted less than 3 minutes each, you can see in the graph they held the temp then just gave out and never pulsed again.[attachment=0]Screen Shot 2019-12-20 at 9.00.13 PM.png[/attachment]

    #1251
    dandan
    Participant

    No chance they’re getting more smashed than they should? No less than 5amp 240vAC should be used. SSRs shouldn’t die that quickly. If failing in an closed state (on) might be a good idea to install a suitable thermal fuse in the live line.

    #1252
    phongshaderphongshader
    Participant

    Quote:

    No chance they’re getting more smashed than they should?

    Not sure what you mean. I’m running 120vac on a 15 amp breaker. I don’t know what the bed is pulling amperage wise. The SSRs are failing in a closed state but I’m still using the thermostat that came with the bed as a limit to how hot the bed can get.

    I did a little research and the market is flooded with fake Fotek SSRs that are rated much lower than advertised and it’s hard to find a legitimate source other than Fotek. Shipping from Fotek is half again more the the price of the SSR. I bought a USA made SSR which was a bit more than the Fotek but less than the Fotek + shipping. I haven’t received it yet so no info as of yet.

    #1253
    phongshaderphongshader
    Participant

    Quote:

    No chance they’re getting more smashed than they should?

    Not sure what you mean. I’m running 120vac on a 15 amp breaker. I don’t know what the bed is pulling amperage wise. The SSRs are failing in a closed state but I’m still using the thermostat that came with the bed as a limit to how hot the bed can get.

    I did a little research and the market is flooded with fake Fotek SSRs that are rated much lower than advertised and it’s hard to find a legitimate source other than Fotek. Shipping from Fotek is half again more the the price of the SSR. I bought a USA made SSR which was a bit more than the Fotek but less than the Fotek + shipping. I haven’t received it yet so no info as of yet.

    #1254
    phongshaderphongshader
    Participant

    I got the new SSR, the heated bed stays right on temperature and the SSR doesn’t even get warm. I guess you get what you pay for :D

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