LIMESDR HEATSINKING UPDATE: Recently, I purchased (among other things) a kit of heatsinks for the Raspberry Pi from MCM Electronics, the stock number for that kit of heatsinks was: 83-17617 and they were $3.99 for the kit. Many places provide a similar kit if you cannot order from MCM Electronics or have a source closer to you. From the pictures you’ll note the kit itself and then the ‘Before’, ‘In-Process’, and ‘After’ shots of the LimeSDR being outfitted with those heatsinks - both of them are adhesive (self-sticking). I placed them on the FPGA and the actual RF ASIC in this application - the two devices that often are the hottest running on the LimeSDR board. Once I completed the installation on my LimeSDR, I ran the board for several hours and noticed that it ran MUCH COOLER as a result. It used to be that I could feel the heat on the top cover of the case, but with the heatsinks I noticed that not only was the case much cooler, the heatsinks were REALLY pulling the heat off both devices. I would highly recommend this modification for anyone that anticipates using their LimeSDR a lot in the shack or are running it for extended periods of time. 73 de Marty, KN0CK
I’m using heatsinks for RPI from Conrad:
73 de Sabine, OE1YVW
There are heatsinks the exact size of the chips readily available in Ebay. Most come with silicone pad or paste. Just measure and search.
The challenge is removing the heat from inside the enclosure without big holes and fans. Temperature can reach >90ºC easily.
add a small fan to your housing
lime has a fan connector onboard
but does a fan make RF NOISE when placed inside the housing?!?
then you should mount the fan outside the housing and use a metal screen (net or a number of holes that should be small)
Wrong answer huh?
Hi, this is my approach to combat heat in LimeSDR. I’ve used heat sinks bigger than the FPGA and LMS7002 chips which gives bigger surface to dissipate the heat as well as 4 smaller ones but in my tests I’ve noticed that best results are provided by using thermal silicon pad between the PCB and metal case. Together with radiators this setup allows me to have 38C (with 18C ambient) reported by Lime Suite after an hour of board operation (so far this is the highest temp I’m getting). Using just the radiators the board was going around 50C therefore I really recommend using a silicon pad. As you can see in the picture PCB is firmly screwed to the bottom part of the case which makes sure silicon pad is nicely sandwiched between the board and the case. At the moment I use the device with open case but my plan is to drill a lot of small holes in the top case part and enclose it completely. I was also planning to add an additional fan on top of all this but it looks like it might be completely unnecessary as I’ve read somewhere on this forum that thermal control software it’s not going to turn on the fan if the temp is below 55C.
All very nice moves everyone!
The Silpad on the whole bottom thing is a great idea and it got me thinking that if heat sinks that are tall enough to nearly touch the top of the case were installed and a Silpad at the top tying the tops of the heat sinks directly to the case thermally even greater heat control gains might be made as well as providing some top bracing for the heat sinks making it a bit tougher.
I’ve found some suitable candidates and am ordering them, I am getting them a little taller so I can machine them down to fit.In the meantime I’ve had no heat issues as long as the Luftek ended case was sitting vertically on it’s side, seems to move the heat off the parts with the sensors all on it’s own.
I saw this silicon pad material but have never tried it. Sounds like a good solution but I don’t know if it’s safe to apply directly to the PCB and exposed parts.
I’m very interested by your solution :), well done by the way.
Could you please put the links of the heatsinks and the silicon pad you used ?
All ot the elements were bought on ebay, here are the links
This one needs to be modified by cutting off one row of pins
You would also need thermal adhesive like the one below as only the smallest radiators comes with it
This is the thermal silicon pad I’ve used but it’s quite thick (2mm) so probably something thinner like 1.5 or even 1mm would do the job even better it probably depends on the hight of the biggest parts on the back of LimeSDR so you have to measure this.
I hope this helps, good luck cooling down your SDR
Thanks for the ping - @nrg-fv did a great job of identifying several on EBay that will work fine. I bought mine from MCM Electronics in Ohio and those heatsinks were fit-perfect for the Raspberry PI, but I used them for the LimeSDR as well for the LMS7002 and the FPGA. There are other parts that get rather warm and @SabineT has illustrated in this thread what she used - that was a good application, too. Here is the link to MCM where I got mine:
Again, if you’re not stateside US, the other sources that have been provided by others on the thread will work equally as well. Also I only used the thermally conducted adhesive that came with the heatsink and it worked fine with the LimeSDR. I’ve had mine plugged in for DAYS and running and I have had no failures whatsoever.
Thanks again for the ping and hope this information will help you on your way to getting the devices cooled for the LimeSDR.
73 de Marty, KN0CK
I just chopped up a heatsink from an old video card to suit the chips on the lime. Works a treat. I used the self adhesive thermal pads to stick them on. Got heatsinks on USB chip, regulator, fpga and lms7002. I’m using a 6mm think silicon thermal transfer pad on the bottom of the board which draws heat away to cast aluminium case. No forced air cooling and my lime rarely goes over 35 deg C even during extended tx sessions (1/2 hour +).
I already have all the necessary parts for my case. I have a generic aluminium box, luftek’s panels and some pigtail SMA to UFL adapters. Sadly my LimeSDR only ships in the end of the month (that’s why I have been so inactive lately).
I also have a pair of old Pentiums’ (those old Pentiums with MMX technology, picture below) heatsinks with a low profile fan. That’s what I’m planning to use. I’m also planning to buy some of those cheap raspberry heatsink kits for ebay if needed.
@FFY00 - Filipe,
Hang in there and we look forward to seeing your posts when you get active with your Lime…! Exciting times with all the development that’s happening with the LimeSDR for anything between HF to SHF right now…
73 de Marty, KN0CK
I have a couple questions. What did you purchase to make your case for your LimeSDR and what type of u.FL connectors are those.
Also, would you recommend putting a heat sink on any additional components.
@nuszkowskir - Ricardo,
The split case LimeSDR enclosure now has a fan which is even better - that can be found here:
…and if you don’t want a fan on it, here is the other alternative:
The U.FL connectors I have been using are here:
You’ll have MORE than you need, but they are a bargain at this price and I’ve used them without ANY issues at all. Chances are good you’ll need them for another LimeSDR you’ll add to your existing Lime down the road…
I would highly recommend using heatsinks with your LimeSDR, but I only heatsinked the FPGA and the LMS7002 device - nothing beyond that and I’ve run my LimeSDR for (what seems like) days at a time. You can buy those heatsinks on EBay, too:
Let me know if you need anything else, Ricardo -
73 de Marty, KN0CK
Thank you so much! Is there anything that can interfere with the SDR with using a fan on the case?
@martywittrock I do have a quick question, for the alternative case without the fan. Does it come with all the same components as the unit above (just without the fan)? Or does it just come with the outside shell structure and we would have to buy all other components separately.
Also, would these work if i purchased these: https://www.ebay.com/itm/171598054838?var=470590537181
I just did not know if the IPEX made a difference.
@nuszkowskir - Ricardo,
From what I can tell, it’s designed to not have interference with any LimeSDR parts with the fan installed.
73 de Marty, KN0CK