LE minus heatsink

[DonFL]

Can anyone confirm the spec'd per channel current handling capability for the Express without a heat sink?

I've got a bare board and no heat sink, and not real keen on fabbing my own. Not sure if RJ sells just the heat sink on its own at any time, but with my display, I seldom draw over a 2A per channel anyway.

Considering the heatsink spec of 4A/channel, and the triac, if I recall, is a 6A device, I have to believe I'm definitely safe with a load under an amp, and probably ok at 2A max.

(And yes, if anyone has an orphan heatsink lying around that they want to send to a good home, I'm a buyer... )

[TexasStingray]

I know the store is out of PCB's with heats inks. When they come in I would order one and keep the PCB as a backup just in case. I personally would not use it with out the head sink as RJ designed them to work with a heat sink. From the past 2 years I have seen Express Coops get started in January if you can wait I sure would.

[tbone321]

I agree with TexasStingray about checking the store to see if a heatsink is available or if he plans on ordering an extra's the next time a coop runs.  The SSR4 doesn't com with one and it is good for about 1A per channel.  I would suspect that the Express would be about the same BUT if you assemble it without the heatsink, it would be near impossible to add it later.  Since the season is pretty much over for this year, it would be better to send out a PM or two and see if a heatsink becomes available before building the unit.  Once assembled this way, it's usefullness and value to others will be extreemly limited.

[DonFL]

If I were to build it this way it would be because I can use it that way, no intention of trying to add a heat sink later.

And yes, parallel to this thread, getting my hands on a heatsink is the hope.

Thanks for the feedback.

[scharbon]

Send me a PM, for the cost of shipping, I can send you a heat sink.  It might not get in the mail until next week, if that is an issue for you then this may not be a viable option. 

As for what can an LE handle without a heat sink?  I am running mine pulling no more than an amp on a channel and never more than 6 AMPS total and it has never been a problem.  YMMV. 

I think it can handle more - there is a thread on the topic which I cannot find, but this is at least a working lower bound on performance without a heatsink.

Steve

[JonB256]

I know that the big, red Lynx heat sink is an impressive sight, but if you are running LEDs only, or 100 count strings of incandescents (1/3 amp each), then it can be left off.

Alternatively (and I did this on some of my non-Lynx AC controllers), a thin bar of Aluminum from Home Depot with 16 holes drilled into it, will boost the power dissipation capacity a lot.

If you've already soldered in the TRIACs, you will have a hard time mounting the Lynx heatsink because it is precision drilled.

[DonFL]

I tend to agree with you re that rough idea of "heatsinkless" load that the LE can handle.

The board is sitting bare, still need to order a BOM of parts, so long way from being at the point of needing the heatsink.

[rrowan]

Well I went searching for the answer

RJ has stated that 2 amps max without heat sink. I have updated the wiki assembly manual to state that also

Rick R.

[DonFL]

Thanks for confirming!

[rm357]

The ssr4 uses the same triacs and is spec'd at 1 amp per channel without a heat sink and 2 amps if you add a piece of angle iron. Since the express has a lot more room between the triacs (more space for air circulation/cooling), you can probably get away with a little more than that with no issues.

[chrisatpsu]

plus the traces for the 120v on the express are much larger than the ssr4 has.

[rm357]

I didn't think about the traces - they will help wick some of the heat out of the triacs - thus RJ's recommendation of 2 amps...

The great thing about the lynx heat sink is that it is really attractive when you open the box. Any chunk of aluminum or even angle iron will help dissipate the heat. The 4 amp per channel limit with a good heat sink is due to the physical size/thickness of the traces on the board...