Hi everyone,

I'm an amateur at electronics, so this question may be a bit stupid. I have a linear drop-off regulator which is reaching temperatures of about 60 C. This seems dangerous to me, so I'm going to try attaching a heat sink. However, on other forums online I've read about things like sizzle tests (seeing if licking your finger, then touching the component, causes sizzling), which seems to indicate that temperatures around 60 C are not that uncommon or dangerous. What kind of temperatures are safe for electronic components? This particular project is a decorative piece that's meant to be kept plugged in on an endtable.

Thanks!

 

I have a linear drop-off regulator which is reaching temperatures of about 60 C. This seems dangerous to me, so I'm going to try attaching a heat sink. However, on other forums online I've read about things like sizzle tests (seeing if licking your finger, then touching the component, causes sizzling), which seems to indicate that temperatures around 60 C are not that uncommon or dangerous. What kind of temperatures are safe for electronic components? This particular project is a decorative piece that's meant to be kept plugged in on an endtable.

The manufacturer's data sheet for the regulator will tell you what operating temperature range is acceptable; but if the case temperature of your regulator is actually reaching 60 °C then I'd seriously consider using a heatsink anyway. Better safe than sorry.

 

What kind of temperatures are safe for electronic components?

120c (die temperature) is fairly common and some are rated 150c.

typically, if the case is too hot for your fingers to hold onto it, it is too hot.

 

It sounds like the temperature is acceptable, but a small heatsink should improve reliability.

 

All this can be done with the proper math, but one needs to know which chip number, how big the case is, what the datasheet says, how much current and how much voltage. With you having provided none of these, all we can do is guess: If it's too hot to touch, give it a heatsink.

 

Although 60deg C is OK, the device will be more reliable if you add a heatsink so that it runs cooler. Although you should do the maths, the actual thermal resistance to ambient is hard to calculate. It will be affected by things like airflow, ambient temperature, altitude, etc. It will change a lot if you enclose your circuit in a case.

My "rule of thumb" (literally in this case) is if you can hold your finger on it for a minute without pain, then its not too hot! If not, use a heatsink.

 

Most modern monolithic voltage regulators (LM340, LM317, LM78XX, etc plus the negative voltage versions) that do not have an over-temperature shut-down function. That means that if you are getting the expected voltage out, the regulator thinks it is just fine.

Check the datasheet for your regulator to confirm it has over-temperature (or thermal) shut-down.

On the other hand, if the regulator is exposed such that skin contact is a significant risk, take steps keep the temperature below 60° C to avoid 1st degree burns or worse.

 

Although 60deg C is OK, the device will be more reliable if you add a heatsink so that it runs cooler. Although you should do the maths, the actual thermal resistance to ambient is hard to calculate. It will be affected by things like airflow, ambient temperature, altitude, etc. It will change a lot if you enclose your circuit in a case.

My "rule of thumb" (literally in this case) is if you can hold your finger on it for a minute without pain, then its not too hot! If not, use a heatsink.

Your rule of thumb is too conservative.
If you can hold you thumb on the device for a minute without getting burned then the temperature is likely no more than about 45°C(113°F)
Most silicon semiconductors will run at 70°C junction temperature or more with good reliability.