Dead SSR heatbed wont heat no more
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In the last week i printed a lots working on another star war helmet , printer was working yesterday but had to stop it because of a mistake of my own , today i open it up to print again after fixing the print file lol ! . The bed wont heat up start checking wire and all with tester , seem like the SSR 40a relay failed , light show the gate as open but cannot get any voltage across , so it dead . Back to finding a better one this cheap one lasted around 6 month. I went looking at the duet wiki for suggestion couldnt find the exact model from Auber instrument but settle for these 2 :
ended up ordering this 80A DC SSR (50V), Low On-Resistance, High Switching Speed, PWM
https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=674
and this one as well
https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=288
didnt seem like they had lower AMp rated one unfortunately . That heatbed overall as always been a pain. Ive try 2-3 different model of mosfet and they always ended up failing quick or get really hot that they fail . really curious of trying that that PWM SSR hopefully it work and fix my problem and lasted for a long period of time. Cheap SSR of amazon are sketchy ....
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@dad003 what is the specification of the bed heater?
Make sure that you set the PWM frequency for the bed heater low in the M950 command that sets up the output, for example use Q10 to set it to 10Hz.
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Is it an AC or DC heated bed?
For AC, I use this one: https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=30
For DC I have this one, but never ended up using it: https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=288
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A few dumb questions:
- Is the heater LED on the main board flashing or at least lit?
- Have you disconnected the heater and checked continuity/resistance?
- What resistance was measured?
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Sorry for the late response didnt had much time lately and i got this week the new SSR from auber
Swapped out the SSR and all is good now . it was just the cheap SSR that was causing the problem.
Checked the config as well added "Q"parameter at the M950 for the bed heater didnt had it apaprantlyThe high switching speed allows this SSR to be operated in pulse width modulation (PWM) mode up to 2 KHz.
Here the next question which number should be optimal for the "Q" parameter since this SSR can do a pwm of 2KHz ?
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Assuming your bed has significant thermal mass you don't need to worry much about switching speed.
I use Q10 on all my bed heaters which are heating 6mm of aluminum and have seen no reason to change it.
Frederick
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@fcwilt okay thank you
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@dad003
Could have sense cool it down ... also if the peak is higher just at the start of the heating. At least it will not be stressed. Maybe will last much more.
(ex not cooled on 12V 28A 340Watt - SSR 60A DC/DC - placed on a small aluminium bar)
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I solved in a old style way
https://forum.duet3d.com/topic/24785/cooling-ssr -
@giostark it was on a aluminum heatsink , it was never hot either has well when i checked it , it was just a cheap bad quality ssr
