Suitable and cheap heatsink - Page 1
Forum section: electronics / beginners

author: VEGETA
author_rank: Super Contributor
timestamp: November 08, 2018, 01:01:09 pm
content: Dear friends,I have a project to make electronic load which is 30v 2A only, but I plan to make it 30v 5A with a max of 150W in the future.Will this heatsink be enough:https://www.aliexpress.com/item/1-PCS-100x41x8mm-Aluminum-Radiator-Heat-Sink-Heatsink-for-Computer-LED-Amplifier-IC-Transistor-Computer/32914236957.htmlI only want cheap stuff from aliexpress especially for shipping, if I am fortunate enough to be able to sell it in future.I am open to use a cheap 12v fan or so if it helps.

author: GeoffreyF
author_rank: Regular Contributor
timestamp: November 08, 2018, 01:04:53 pm
content: Any piece of heat conductive metal such as aluminum or copper is fine. If it is made with fins, that's better. If it has no fins, make it a little bigger.

author: CJay
author_rank: Super Contributor
timestamp: November 08, 2018, 01:11:08 pm
content: No idea, the specs on there relate to a fan, not a heatsink and your specs are pretty vague too, you need to know specs for the devices you're going to mount, decide on an acceptable max temperature over ambient for the heatsink and a few other things.You could find a similar size heatsink from a supplier that gives proper specs and assume they're approximately the same, then do the heatsink calculations (which are pretty simple)Gut feeling is that yes, it'd probably do but it'd be useful to you in the future to be able to specify and design it properly.

author: hayatepilot
author_rank: Frequent Contributor
timestamp: November 08, 2018, 02:19:52 pm
content: The linked heatsink is way too small for 60W let alone 150W!!It is only 8mm high.Just look at how big a CPU heatsink is, which dissipates about the same power.This heatsink is the size you would need:https://www.dhgate.com/store/product/50-150w-high-power-led-heat-sink-led-cooling/176904642.htmlAnd it needs a fan too for full dissipation capacity.Greetings

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 08, 2018, 04:30:40 pm
content: Bear in mind it's the sum of the thermal resistances of the device itself, its case, any mounting washer and the h/sink that have to be added to determine the power rating. Just fitting a larger h/sink to an underrated device soon gets into a law of diminishing returns.For this kind of duty, avoid TO220 devices as you just can't get an adequate thermal bonding to the h/s on so small a case. TO247 or TO3 will be a better bet, though even so one would be stretching things, think in terms of at least two in parallel.Going fan assisted will definitely lead to a smaller and probably cheaper unit than a monster convection h/s. Thermostatic control them becomes preferable to avoid too much noise on light loads. Although that does call for a separate fan supply, of course, which convection cooling avoids.

author: VEGETA
author_rank: Super Contributor
timestamp: November 08, 2018, 07:45:50 pm
content: I ordered one and another different one to test them. I will mount 4 N-Mosfets IRILZ44N (isolated package) on it, I already ordered the threading tool too.right now it is only 60W for this project but the future upgrade must be 150W.I will put everything in aluminum enclosure of 100x100x50 mm dimension.

author: hayatepilot
author_rank: Frequent Contributor
timestamp: November 09, 2018, 10:06:45 am
content: Please let us know your results/temperatures.Imho that heatsink is too small for a sustained full load. You might get by for a minute or two at full load.Greetings

author: VEGETA
author_rank: Super Contributor
timestamp: November 09, 2018, 01:33:31 pm
content: Quote from: hayatepilot on November 09, 2018, 10:06:45 amI will do Inshalla.I am not really confident that this will be enough, but for now, it might be suitable for the 30v 2A version.

author: mvs
author_rank: Frequent Contributor
timestamp: November 09, 2018, 02:41:04 pm
content: Quote from: VEGETA on November 09, 2018, 01:33:31 pmI use 20 cm²/W as a rule of thumb for passive cooling. With ~350cm² heatsink from your first post, this mean 17.5W cooling capacity.With a fan this heatsink will be probably sufficient for 60W, but I would recomend you to use some CPU Cooler instead.