Initial Config Query
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@jay_s_uk
Here are my drivers and how I’ve wired them as recommended by Duet -
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@chrishamm Thanks for the advice added this to my config but Im still having the same issue.
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@chrishamm I should note I do also currently have bang-bang mode enabled on the config.
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@900turbo Please check your SSR, it looks like it does not turn on. If it does, the connection between SSR and your heated bed may be dodgy. Also, you should tune your heaters before you actually try to use them or you will get more heater faults.
Note that the heater should turn on as well as soon as you start heater tuning.
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@chrishamm Checked my SSR with a multimeter and its reading 0.8 which suggests it Is not burnt out. I have gone back over the connection to the heated bed and there is no damage or exposed wiring or a open circuit. So I am a bit lost as to what's wrong.
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@900turbo Does the LED next to
out0turn on when you start heater tuning? And do you measure Vin or 12V across the inputs of the SSR while it's lit? -
@chrishamm The LED next to out0 does turn on. I should note the heated bed is extremely big 700x700mm could this have any effect? What do you mean by that is in take those measurements whilst the SSR is on?
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@900turbo It depends on the power of your bed heater but there should be at least some temperature rise, which is not detected by the firmware. Hence my suspicion that the control signal from the Duet does not turn on your SSR. That's why I suggest to check if there is enough voltage across the control input of the SSR to make it turn on.
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@chrishamm just checked the SSR is getting 21.9 V more than enough to turn it on not just that but its green LED is constantly on suggesting its receiving more than enough power to function properly.
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@900turbo
Here is the entire Heater Config
; Heaters
M308 S0 P"temp0" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin temp0
M950 H0 C"out0" T0 Q10 ; create bed heater output on out0 driven at 10Hz and map it to sensor 0
M307 H0 B1 S1.00 ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0 ; map heated bed to heater 0
M143 H0 S70 ; set temperature limit for heater 0 to 70C
M308 S1 P"121.temp0" Y"thermistor" T100000 B4725 C7.060000e-8
M950 H1 C"121.out0" T1 ; create nozzle heater output on 121.out0 and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
M143 H1 S300 ; set temperature limit for heater 1 to 300C -
@900turbo So how much power does your bed heater have? How long does it take with the heater turned on before you can actually see a difference in temperature?
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@chrishamm How would I find that out ? Nothing happens when you try to raise the temperature I get this notification.
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@900turbo Check the resistance of the bed heater and check if there is sufficient input voltage to drive it. To see if it does anything, you could use a manual switch instead of the SSR and check if the bed heater gets warm at all. If it does, you should see a temperature increase on the web UI as well.
The firmware does not see any change in temperature indicating that your bed heater element is not working. Your config and SSR input voltage look fine to me.
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@900turbo I've only had a quick scan through this thread so I may have missed something, but it seems to me that the SSR is being turned on but that the heater isn't actually heating. Which would indicate that there is no power reaching the heater from the output side of the SSR - or the heater itself might be faulty. As @chrishamm has said, the first thing to check would be heater itself. Without any power, disconnect the heater and check the resistance across the two wires. We'd need to know what the rated voltage and wattage of the heater is in order to calculate what the resistance should be. As an example, for a 700mm x 700mm build plate, I'd assume something like 800 watts? If it was 240 V then the current draw would be about 3 amps so we'd expect a resistance in the order of about 3.3 A which would mean the resistance ought to be in the region of 80 Ohms. But we'd need to know the actual voltage and wattage specification of the heater to calculate roughly what resistance it should be. If the resistance is about right, check the voltage across the heater itself but be very careful as you are likely dealing with mains voltage.
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@chrishamm The bed heater is giving me a resistance of 147.9 , how would i check the input voltage?
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@deckingman
Thanks Ian , I believe the SSR is turning on , I agree it seems no power is reaching the heater beyond the SSR output. I did look into the bed and there was no markings or serial numbers however previously I asked about this in the forum.
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@900turbo "check the voltage across the heater itself but be very careful as you are likely dealing with mains voltage." How would I do this correctly?
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@900turbo @chrishamm
This may help but thought I’d show a photo of what’s going on control wires on the SSR input running to the MB , then the power from the SSR output to the heated bed and another power running into a relay and then the PSU. -
@900turbo said in Initial Config Query:
@900turbo "check the voltage across the heater itself but be very careful as you are likely dealing with mains voltage." How would I do this correctly?
With a multi-meter at the same point that you measured the resistance but be careful as you are likely dealing with mains voltage. If you are in any doubt about your competence, ask an electrician to do it for you.
You haven't told us if this is 110V mains as used in the US, or 220 -240 V as used in the UK and Europe. But using your measured 148 Ohms resistance, from Ohms law we can deduce that the current draw is 1.6 Amps if using 240 V and 0.7 Amps if using 110V. Wattage is voltage x current so we can say that if using 240 V, the wattage is around 390, and if using 110V, then it is a mere 81 Watts.
If the bed is 700mm x 700mm, then it would need to reasonably thick so I'd say that the heater is under powered for this application. There are formulas for calculating the heater power required - do an internet search. But as a guide, I use a 400Watt heater on my 400mm x 400mm x 10mm thick bed and your 700mm x 700 mm bed is 3 times the area, which would indicate that you ought to be using around 1200 watts.
