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24V Upgrade to my Max V3

Posted: Tue Oct 04, 2016 5:00 pm
by Noircogi
Most of this is copied from another thread. Just putting it here to help others.

After building my Max V3, I was surprised how weak the bed heating performance is in a stock config. Mine would never go over @95C without a washcloth on the bed. You can turn the power supply output voltage up to 14V and it will eventually hit 100C but still takes a long time. (That keeps you below the 15A bed heater fuse limit). I measured my Onyx with a high-end multimeter and it is 0.92 Ohms. Power measurements also bear out that number. That's a lot lower than I've read other places for the Onyx btw.

I ended up buying a 600W 24V PS, a Crydom 40A DC/DC solid state relay to drive the bed and a 20A 12V step-down regulator to drive everything else.

Turn the voltage on the power supply down to 20.5V to limit the bed heating to around 450W and make sure to put a fuse on that circuit. Now it will go from 25C to 100C in about 3 minutes.

DO NOT buy a Fotek or SHZE SSR, even with a heatsink, thermal paste and good airflow they will heat up and fail very shortly (I know from experience). When they fail, they fail in the "ON" state so it's a fire hazard. Luckily I was watching closely. They have far too high of internal resistance to meet their spec in any reasonable install. Get a MOSTFET-based one like a Crydom or Auber with an ON resistance of around 0.006 ohms or so.

I ended up buying a 40A Crydom from Digikey: https://www.digikey.com/product-search/ ... =CC1860-ND which doesn't even get warm during use (with heatsink and airflow), but I believe the much cheaper Auber 100A has similar impedance: http://www.auberins.com/index.php?main_ ... cts_id=288

I mounted the SSR on its heatsink in the front of the base, right behind the front panel. I cut a small hole in that panel so it, the power supply and the regulator get great airflow from the stock base fan. The regulator is slightly behind and to the right of the SSR. It seems to stay fairly cool during operation as well. The power supply is mounted in the stock location. It's slightly wider than the stock one, so you need to just screw it to the base plate,

The only down-side is that idle power (at the wall) went from 11W to 18W due to the new PS and the step-down regulator.

THese are the other parts I'm using:
Heatsink: https://www.amazon.com/dp/B00ARBA02A/re ... R+heatsink
Regulator: https://www.amazon.com/gp/product/B00BW ... UTF8&psc=1
Fuse holder: https://www.amazon.com/gp/product/B00NQ ... UTF8&psc=1
Power supply: https://www.amazon.com/gp/product/B019R ... UTF8&psc=1
Thermal pase: https://www.amazon.com/Zalman-ZM-STG1-S ... rmal+paste
I used a small terminal block to connect the 12V wiring to the output of the regulator.

The power supply seems to be working great so far even though it's a cheap one.

I used some #8 x 3/8" sheet metal screws to attach those parts inside the base plate.

I also blocked all of the air vents in the base plate with gaffers tape so the base fan won't draw the hot air out of my enclosure.

Re: 24V Upgrade to my Max V3

Posted: Fri Nov 18, 2016 3:20 am
by teoman
If you blocked all the air vents then you will end up with heat buildup in the bottom.

It may be a better idea to insulate the bottom of the bed. (Some have done it eith aerogel).

Re: 24V Upgrade to my Max V3

Posted: Fri Nov 18, 2016 1:06 pm
by Noircogi
I blocked the vents between the chamber and the bottom, also between the chamber and the top. I opened a hole in the front of the base, right in front of my SSR and its heatsink to allow cooling air in for the SSR and power supply. I moved the top fan and opened another input up there also. The base is fine. The enclosure gets up to about 40C eventually.

I added a fan controller in the base which controls the base fan's speed based on a thermistor attached to the power supply, so the base fan ends up running much slower and quieter most of the time as well.

Re: 24V Upgrade to my Max V3

Posted: Tue Jan 17, 2017 11:07 pm
by NormL1
Noircogi, stupid question, but, could you do a quick wiring diagram as I am not really sure how to wire up the Auber relay.

Re: 24V Upgrade to my Max V3

Posted: Wed Jan 18, 2017 4:46 am
by DeltaCon
Voila:
24VHeatBedConsComment.jpg
Read this thread, it has LOTS of info on the subject!
http://forum.seemecnc.com/viewtopic.php ... &hilit=24V
There is no real difference between V1, 2 or 3 in this regard.

Re: 24V Upgrade to my Max V3

Posted: Wed Jan 18, 2017 10:41 am
by NormL1
Thank you!

Re: 24V Upgrade to my Max V3

Posted: Wed Jan 18, 2017 3:02 pm
by DeltaCon
To add:
- Discussion here lately has been that it is better to connect the SSR on the hot side (24V side) of the PSU. That seems reasonable.
- Recently I have found an advice to make a seperate circuit with a 150C thermal fuse thermally glued to the bed, that keeps a normally closed relais open. In case of overheated bed (or elseway failing machine causing fire) the power to the machine will be cut. Seems like a good idea too. Especially with an SSR that fails in an open state (fotek). It was not my idea, but I am too lazy to check who's idea it was ;-). Credits are not mine!

Re: 24V Upgrade to my Max V3

Posted: Wed Jan 18, 2017 4:12 pm
by Xenocrates
You have the relay backwards. You want a Normally open (NO) relay that will break the circuit. I don't think it was my idea exclusively, but I seem to be the first person I can find on the forums for it.

Re: 24V Upgrade to my Max V3

Posted: Thu Jan 19, 2017 3:56 am
by DeltaCon
Xenocrates wrote:You have the relay backwards. You want a Normally open (NO) relay that will break the circuit. I don't think it was my idea exclusively, but I seem to be the first person I can find on the forums for it.
Of course, excuse me. I am confusing relays with watertaps. When a tap is open, water flows, a relay works the other way around ;-)
I guess I should leave electrical comments to you :oops:

Re: 24V Upgrade to my Max V3

Posted: Thu Jan 19, 2017 11:07 am
by Xenocrates
DeltaCon wrote:
Xenocrates wrote:You have the relay backwards. You want a Normally open (NO) relay that will break the circuit. I don't think it was my idea exclusively, but I seem to be the first person I can find on the forums for it.
Of course, excuse me. I am confusing relays with watertaps. When a tap is open, water flows, a relay works the other way around ;-)
I guess I should leave electrical comments to you :oops:
It's not a huge mistake. I've nearly made it many many times (Thank you, Edit comment feature). I tend to think of it as passing/not passing until I get to actually writing it out.

Re: 24V Upgrade to my Max V3

Posted: Sat Jan 21, 2017 6:23 am
by DeltaCon
This is how I usually solve problems...
ElectricGardenhoseLead.jpg
ElectricGardenhoseLead.jpg (6.97 KiB) Viewed 8808 times

Re: 24V Upgrade to my Max V3

Posted: Sat Jan 21, 2017 10:56 am
by Xenocrates
DeltaCon wrote:This is how I usually solve problems...
ElectricGardenhoseLead.jpg
I use the HDMI version myself. Makes sure I get very clear water with no scanlines, and nice audio too. [img]https://s.yimg.com/lo/api/res/1.2/pSIgB ... jpg.cf.jpg[/img]