24V Heatbed with SSR
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I am officially stumped! Obviously the output of the Duet works as it is supposed to. Since the SSR switches fine with a 12V signal from the power supply but DOES NOT switch with the same 12V signal from the Duet, this just isn't possible.
I would try to replace the SSR but chances are you haven't got a spare one sitting around and this is REALLY a long shot.Maybe somebody else has some other ideas. In any case, please keep us posted what the fault turns out to be.
Sorry I can't be of more help.
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Thanky you for your help. I will double check all again. Maybe I make a mistake.
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I found out that when I connect the 12 V directly from the power supply to the control side of the SSR, the bed heating up and I can masure 1V between the plus and minus of the SSR(24V) main side.
If I connect the SSR to the duet bed connector and switch on the bed I mesure 24V between the plus and minus of the SSR(24V) main side.
Make this sence?
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Yes, it makes sense.
In the first case the SSR switches on so you have only a small voltage drop across the SSR.
In the second case the SSR stays switched off so you see the full 24V across it.
It just is really odd that you would get the LED on the SSR to go on (as in the second case you are describing) but yet the SSR itself stays off.
It's a weird one alright .... -
Yes, the LED is relly on.
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When you command the Duet to turn the bed heater on, does the bed heater LED on the Duet light up?
Is the Duet reporting the correct bed temperature?
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The Duet is reporting the bed temperature, if it is really correct I can check tomorrow.
I check today evening, if the LED light up. Is it possible the the LED on the SSR is on and the
LED on the Duet is off?
What does the LED indicate? -
@omerkel said in 24V Heatbed with SSR:
The Duet is reporting the bed temperature, if it is really correct I can check tomorrow.
I check today evening, if the LED light up. Is it possible the the LED on the SSR is on and the
LED on the Duet is off?
What does the LED indicate?The LED indicates that the Duet is providing power to the bed heater output terminals.
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Since the light on the SSR is on, but no power gets switched to the bed, I can only imagine a problem with the SSR. Is it really an SSR or are you using something else to relay? I don't know if it is even possible for an SSR to not be able to handle the switching frequency, but on the other hand, when duet starts heating the bed it will be at full power, so no switching at all...
Maybe try to reverse the + and - on the 12V side of the SSR. Maybe you are reversing that when switching from DUET control to continuous 12V control?
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@jens55 said in 24V Heatbed with SSR:
Seems odd but ok.
Not as odd as you might think. Lot's of people have 12V machines but upgrade to 24V beds. One way is to go double PSU. Personally I got myself a capable 24 PSU and put everything 12V through a Stepdown converter. I am still switching the bed through SSR because the control board would probably get fried by the high current.
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Tomorrow I will get a new SSR and then test it again.
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While there is no real need for an SSR it can be done.
I have an anycubic chiron wired like that (because that is what was already there when i added a Duet board), with a separate 24v supply to the main output of the SSR and the board only feeding a "signal" to the input side of the SSR, as david has already mentioned make sure you have positive and negative on the signal side correct.
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Yon don't need a SSR, because ground bed only is commuted to ground.
The Duet 2 (Wifi and Ethernet) is rated for up to 18A bed heater current, so this is suitable up to 24 * 18 = 432W power, so no need of SSR for 200W.So you could wiring like this :
I have the same things with 5V fans on 24V duet
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I do it in the mean time like your schematic. Next weekend I will do another try with the new SSR.
The option to connect the fans to 5V is also interesting. How do you connect the fans to the Duet and the 5V power supply?
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Same as for the bed.
Connect fan red wire to 5v psu, black wire fan to fan- on duet
https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans#Section_Using_12V_fans_when_VIN_is_24V