Voltage regulator getting hot

OK - I have already used search - But it had no reference of voltage regulator on CAI getting hot,
 
I use 10.3V PS (12V regulated down to 10,3), but find that regulator is getting hot in 1-2minutes. This CAI is supposed to work outside in sun(50C)
 
What should I do? Fix heat sink(how?)
Use Diode to drop another 0.7V? Will it help?
 
No load connected.
Planned load is one humidity sensor and 5x DS1820, 2xSSR from TTL.
 
Nitin

Hi Nitin,
 
That regulator can get hot, if supply power is above 9V.  However, it should work reliably even it is hot.  We had test board directly powered by 12V running for long time and not having any problem.  That chip operating temperature range is from -40C to +125C. 
 
If you like to add a little heatsink, it will help cool it better.  There are heatsink glue or heatsink epoxy to secure heatsink on it.  There are also heatsink for VGA card or DRAM with glue backing. You can stick those little heatsink on it to help cooling it.

What is the part number of the regulator?  It's likely to fit a standard TO-220 heatsink and you can pick them up at RadioShack.
 
Just use some heatsink grease (CPU HeatSink like Artic Silver) but be careful when mounting (using a very small nut/bolt) as I believe that heatsink will now be at potential, meaning it can't touch anything metal.
 
I'll let someone else confirm as I don't use this hardware.

Regulator is LM2940S
That is a surface mount part.
I think you can stick this on top:

http://www.ebay.com/itm/130791989438


or

Ah, OK.  If it is surface mount, my idea is definitely out!

nitin100 said:

OK - I have already used search - But it had no reference of voltage regulator on CAI getting hot,
 
I use 10.3V PS (12V regulated down to 10,3), but find that regulator is getting hot in 1-2minutes. This CAI is supposed to work outside in sun(50C)
 
What should I do? Fix heat sink(how?)
Use Diode to drop another 0.7V? Will it help?

Click to expand...

 
My daughter-board has terminals for inputs, variable gain amplifiers for the analog channels, and (optionally) a TO220 style regulator.
You can use a linear regulator + decent heatsink, or because it has enough room around it, you can easily use one of the drop-in 7805 replacement switchmode regulators.
Then, the webcontrol board is powered through the external regulator rather than via the onboard linear regulator.

How hot is it? If you can put your finger on it for several seconds it isn't too hot. If you put a drop of water on it and it doesn't boil it should still be ok but if its too hot to touch I would try putting some kind of heat sink on it.

You could put more diodes in series with the supply.

And don't try to power other stuff if it is already hot. Use another regulator for them.

Ok - I am keeping it as it is - As I can see the microcontroller with heatsink on is as hot.
 
Its not worth the trouble to put heatsink on.
 
I will run it on 10.3V and will use CAI judgement of not putting heatsink to VR if run by less than 12V

Heatsink on Microcontroller will cool the cpu.  That is very important, since inside microcontroller, traces are much smaller, heat can cause a lot more damage.
Regulator on the other hand with much wider traces inside to handle more current and heat.  However, if you have those little RAM heatsink, tape on on top the regulator will help cool it, especially if you plan to use it in very hot environment.

Ok In field experience -
Regulator is hot, heatsink of mc is hot. Cannot touch for more than 5s. Same temp of both. CAI should take note as its only 40c today. (55c is normal in june jul)

What is of more concern is the capacitor next to regulator is getting equally hot. Its rated 16v. Not good that's all I can say. The board has not failed yet so will keep on checking.

Power supply is good, 10.3vn no ripple.

Please do keep us posted. We have WC board running non-stop for 5 years in our outdoor environment powered by 9V regulated, so far not having any heat related problem.  We have mild temperature here, only a week or two in a year can get up to 105F during the day, mostly under 90F.
 
I have a board on my bench setup running at 11V power, then use a DS18B20 measure its regulator, the temperature is about 66C, I also tried to measure CPU, but not able to make very good contact only got 48C.  From past, we did hear from customer from Arizona hot place where outdoor is 50C during summer, the WebControl board running fine there without any modification.
 
If heat is your concern, due to hotter environment, I would encourage you get a little VGA/DRAM heatsink mentioned above and place on top of the regulator. That will help during hot day.  Please avoid direct sun shine onto the board, or put enclosure under direct sun shine in extreme heat condition.  If your environment could be really hot, it may also worth to have a temp sensor to measure its own temperature and warn you when the board reached 50C or higher.  Please note that although regulator can work up to 125C, the CPU is only rated to work up to 85C. If CPU requiring 30C temp difference to cool it, that means you should not use this board for environment hotter than 55C without some additional cooling, like getting a bigger heatsink or fan blowing.

I have my hot tub wc board outside using 9v for 2 years (in north east PA.) with no heat/cold problems. I have a temp sensor on WC and temps went from 126f to -15f and never stopped and never froze a pipe 

This  has been an interesting discussion.
 
Thermally my most demanding WC design is the greenhouse controller. It is powered via 9V supply through a 1N4002 diode to drop the voltage a little. I'm also stealing 5V from the WC to power some miscellaneous logic. During sunny days internal temperate can get up to 105F even though we put up a shade cloth to control temperature.
 
During the design the regulator passed the "finger"  test so I was not worried about it overheating.
 
Maximum current drain through the WC is about 250ma. I was not aware of the nifty stick on heat sinks. I went ahead an orders some, hard to beat the price. I'll go ahead and stick one on the regulator. It is overkill but cooler is better.
 
/tom

Update - First day - 2 outputs (TTL1 and TTL2) crapped out. Showing 0.3V now.
Temp sensors - Cannot detect more than 1 after a day. (Cat5 cable)
 
 
I believe the mc is slowing getting ion migration (high temperature), not the power regulator.
 
Lesson learnt - Hobby board - Never apply in real life. Failed at 45C (todays highest temp)
 
Sorry CAI - Excellent support - But hobby hardware - This should go along raspberry pi and other arduino stuff - Not as an industrial controller. Please don't market as industrial controller.
 
All the people who were trying to help - This controller was to be used as motor controller for an roof ac unit-30T(evaporator fixed to fins of HVAC). All other electronics work well here at 55C as I choose to have industrial level stuff(Some Chinese but EU branded PLCs are in the same box as CAI controller).
 
Power supply was stable, 10.3V-0.7v(In4001)= 9.6V?(Sorry - couldn't get the MM to the diode pins- But check the SMPS regularly)

TTL output can only be damaged with overload current.  Did you check what kind of current you pull through the TTL output port?
We don't know where did you get the temp sensors.  But DS18B20 should be able to work up to 125C.
 
CPU is made by Microchip and stated in its web site that operation temperature range up to 85C.  We have heatsink on top of the microprocessor to help it cooling.
If the microcontroller is under specified operation temperature limit, it should not failed. We trust Microchip product meets its spec.
 
Now you mentioned your room air is 45C. But that does not tell if the microcontroller at 45C or not.  If you placed board in a box under direct sun shine, its temperature can be a lot higher. A lot attic temperature are much higher than room temperature. CPU normally will need to have 20C to 30C temperature difference to passively cool it.  From our experience with industrial control design, if you expect the system will operate at high temperature, you will need to add active cooling when temperature is high. Using an extra TTL output, you can turn on a small fan to blow air to the top of the board after temp sensor detected 45C.  All the industrial system designs have active cooling for operation at high temperature.  If you look those evaporator and furnace in attic, they all direct some active air flow to cool its controller board. Without proper cooling, any system can fail.