Onyx Temp Limit

[grimmindustries]

I understand what you're saying and I appreciate the advice too.
I've run a couple of prints that have taken 2 -3 hours and the Onyx has stayed at the required temp perfectly.

[RichardMac]

thanks for the advice regarding AC to the onyx bed.
I had already bought a 24 power supply and a SSR (fotek SSR-25 DD) from eBay few weeks ago, had hitched it up last Thursday using the original 18g wires to go to the trigger side of the SSR, and using 14g wires to feed the bed from the 24v power supply through the load side of the SSR.
Thought I was doing everything right.

I thought.

What I had failed to read on the posts from others switching to 24v was the amps the bed would draw. The power supply I had purchased was only rated to 15 amps.
seconds after turning the bed on via the RAMBO the power supply crapped out.

So I pulled out an old computer power supply I had kicking around (300w) and use that till I could get a new 24v rated to the amps needed (my onyx bed v2 is measuring 1.1 ohms).
I hitched it up and found out that the SSR is toast (load in constantly allowing power through) I'm not sure if SSR was bad to start, but it should have been good till 25A.

The main reason I wanted to switch to 24v was not just quicker heat on the bed, but I could not get the bed to 90 and the hotend to 235 at the same time.

Thanks for the links to the two items from ebay, unfortunately the one item does not ship to Canada and the other wants $ 64 for shipping.

[RichardMac]

Would this SSR be ok ?

http://www.automationdirect.com/adc/Sho ... 40-DC-200D

[Eaglezsoar]

Would this SSR be ok ?

http://www.automationdirect.com/adc/Sho ... 40-DC-200D

Yes that would be fine but it should be mounted on a heatsink that looks like this one: http://www.amazon.com/s/ref=nb_sb_noss_ ... 20heatsink" onclick="window.open(this.href);return false;

[Demolishun]

To get the rated performance of ANY SSR it MUST have a heat sink. You most likely toasted the SSR because you did not have a heat sink. 24VDC / 1.1 ohm is 21.8 amps. Well within the rated current of 25 amps for that SSR. Going up in amperage on the SSR will not help unless you get a good heat sink. You also need heat transfer compound similar to what you put on a computer CPU. You can get that compound at most Radio Shacks and maybe Best Buy. There is always online sources too.

[RichardMac]

I did have a heat sink and compound between the sink and the SSR.
The eBay seller confirmed that incorrect parts were used in the SSR ( I think it was a knock off), and refunded my money.
I have ordered a new SSR from different vendor like the one eaglezsoar recommended.
Still looking for 24v power supply.
I did run different wire to the bed as geneb recommended, but still struggles to reach temps.

[nitewatchman]

To get the rated performance of ANY SSR it MUST have a heat sink. You most likely toasted the SSR because you did not have a heat sink. 24VDC / 1.1 ohm is 21.8 amps. Well within the rated current of 25 amps for that SSR. Going up in amperage on the SSR will not help unless you get a good heat sink. You also need heat transfer compound similar to what you put on a computer CPU. You can get that compound at most Radio Shacks and maybe Best Buy. There is always online sources too.

Caution you to look at the internal resistance of the SSR and calculate the power disapation requirement of the heat shink. The heat loss in watts is found by I*I*R.

Some of the larger relays easily generate more heat than a small heat shink can handle. Use a vendor matched set or do the math.

nitewatchman