DUET burnt track - Heated bed no longer working January 26, 2016 10:11AM |
Registered: 8 years ago Posts: 11 |
Re: DUET burnt track - Heated bed no longer working January 26, 2016 12:49PM |
Registered: 10 years ago Posts: 14,672 |
Re: DUET burnt track - Heated bed no longer working January 27, 2016 03:57AM |
Registered: 8 years ago Posts: 11 |
Re: DUET burnt track - Heated bed no longer working January 27, 2016 06:47AM |
Registered: 8 years ago Posts: 10 |
Re: DUET burnt track - Heated bed no longer working January 27, 2016 07:39AM |
Registered: 10 years ago Posts: 14,672 |
Re: DUET burnt track - Heated bed no longer working January 27, 2016 07:45AM |
Registered: 10 years ago Posts: 14,672 |
Quote
PlasticPogle
The repair is holding but I'm looking for a spare board just in case, so if Dave (dc42) has got one or can recommend somewhere, save me the leg work would be appreciated...
Re: DUET burnt track - Heated bed no longer working January 27, 2016 07:50AM |
Registered: 10 years ago Posts: 2,472 |
Re: DUET burnt track - Heated bed no longer working January 27, 2016 09:31AM |
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Re: DUET burnt track - Heated bed no longer working January 27, 2016 11:02AM |
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Quote
rpbh99
Hi. Much appreciate the response I have been getting.
The Duet cannot be shorting to the case as, rather than using tape to insulate, I used a single piece of 1mm rigid plastic. I have also checked everything out again.
Whilst it is working now with a jumper, I am concerned about a re-occurrence. I thought about using the on-board MOSFET to switch a 12 volt relay, thus removing most of the current from the board. I also have some FQP30N06L MOSFETs which I could also use externally instead of a relay, if I new how to safely wire them - I usually use them with a Raspberry Pi which only supplies a 3 volt gate voltage. Any thoughts?
Do you think I should replace the heated bed, as this measures 0.8 ohms, meaning 15 Amps is drawn?
Thanks
Re: DUET burnt track - Heated bed no longer working January 27, 2016 03:31PM |
Registered: 10 years ago Posts: 14,672 |
Re: DUET burnt track - Heated bed no longer working January 27, 2016 03:31PM |
Registered: 10 years ago Posts: 14,672 |
Re: DUET burnt track - Heated bed no longer working January 28, 2016 08:10AM |
Registered: 10 years ago Posts: 2,472 |
Quote
dc42
I think it's quite possible that 15A was too much for the track, even though the mosfet can take more. That track appears to me to be the weak link in the 0.6 heated bed circuit. When I was laying out the heated bed circuit for a controller board design, I found it very hard to make the tracks wide enough to carry more than 12A safely.
Use a wire link between the two terminals on the back.of the board as I suggested earlier to prevent a reoccurrence.
Re: DUET burnt track - Heated bed no longer working January 28, 2016 08:15AM |
Registered: 8 years ago Posts: 11 |
Re: DUET burnt track - Heated bed no longer working January 28, 2016 08:45AM |
Registered: 10 years ago Posts: 2,472 |
Quote
rpbh99
Once again, Thank you.
I have measured the voltage across the heated bed, and also the current flowing to the heated bed. The voltage starts at 11.63 v and settles to 11.68, changing from 0 to 11.68 as the heater switches on and off to control the temperature. The voltage across the input to the DUET is 12.11v with no heat load, and 11.93v with heat load.
The current gave a rather frightening 19 amps.
I have ordered a new heated bed, as I suspect 0.8 Ohms is too low, but am still considering fitting a relay to protect the board, however it has been suggested to me that the input to the mosfet gate, and therefore the output, might be controlled using a high frequency switching to control and output, and a relay would therefore not be suitable. Do you know if the mosfet is used in this manner,, or is it just working as a simple on/off relay?.
Re: DUET burnt track - Heated bed no longer working January 28, 2016 05:36PM |
Registered: 10 years ago Posts: 14,672 |
Quote
dmould
While the hardware is capable of making the bed control PWM, I doubt that the firmware will ever be changed to do so because quite a few people are using a relay or SSR to feed the bed.
Re: DUET burnt track - Heated bed no longer working January 29, 2016 06:08AM |
Registered: 8 years ago Posts: 11 |
Re: DUET burnt track - Heated bed no longer working January 29, 2016 10:33AM |
Registered: 10 years ago Posts: 14,672 |
Quote
rpbh99
To be honest, I don't know how to proceed with the track jumpers
Re: DUET burnt track - Heated bed no longer working January 29, 2016 11:15AM |
Registered: 8 years ago Posts: 11 |
Re: DUET burnt track - Heated bed no longer working January 29, 2016 03:31PM |
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Re: DUET burnt track - Heated bed no longer working February 08, 2016 06:49AM |
Registered: 8 years ago Posts: 10 |
Re: DUET burnt track - Heated bed no longer working February 08, 2016 09:15AM |
Registered: 9 years ago Posts: 1,699 |