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Topic: Voltage regulator failed in Mega2650 R3 - micros damaged? (Read 1 time) previous topic - next topic


From a typical datasheet:  ( http://www.fairchildsemi.com/ds/LM/LM7805.pdf )

• Thermal Overload Protection
• Short Circuit Protection
• Output Transistor Safe Operating Area Protection

So, with all that protection, why did the regulator fail?

Because the failure mechanism was of some other nature? What that might be I have no way of telling but I did list that too high a input voltage or having reverse current flow through a regulator can be destructive to the chip.

Do you not believe what the manufactures datasheet says about their chips when they talk of built in protection features?



OK. There are other reasons for the fail:
1) Unlucky.
2) Angered the transistor gods.
3) Failed to pay protection to the local mafia.

I use built-in protection features on my electronics. They are called fuses. However, when they protect my devices best, they also throw themselves on the grenade.

Arduino micro seems to be working find but the problem is that I cannot connect to the board via USB anymore.

This sounds familiar to me. IC7. But that is just me...
((Vin > 10v) && (usbPower == true))


Dec 31, 2012, 06:09 pm Last Edit: Dec 31, 2012, 06:30 pm by oric_dan(333) Reason: 1
Possibly, the inductive spikes from the stepper motor switching blew the v.reg or
other circuitry. This is why it's always good to use a separate power supply for such
loads. Another likely possibility is accidentally touching 12V to a pin on a 5V part
- easy to do.

Also, for best results, on the power input to the stepper motors, you will want to add
both bypass [0.1 uF] and reservoir [100 uF or more] capacitors at the point where the
external supply connects to the motor driver board, in order to filter motor noise, etc.
You want his whether you're using steppers, regular motors, or servos. They all
generate a lot of electrical noise.

A silly question (sorry but not an electronics expert). My understanding is that
the SMD voltage regulator within Arduino Mega ( NCP1117ST50T3G) drives up to 1A.

Everything the other guys said about overheating the tiny smt v.regs is true. With 12V
for Vin, you can only realistically provide 100-200 mA of load current at 5V without
heating problems.

The question is not silly at all, because the overheating issue is not to be part of the general
info provided in adverts, so it comes up on this forum a couple of times every week, and
has to be explained again and again.

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