Spark on voltage regulator

Hello,

I have a promini 3.3 V .

I connected 2 lithium batteries of 3V 1500mah each ,in series to get 6 V and this was given to the raw pin of the promini.
Initially it was fine. But when I connected it for the second time, there was a spark on the voltage regulator and the componet towards the bottom side in the circle, next to the voltage regulator (figure attached) burnt completely.

(The solenoid requires 5V and 1.2A . I have mosfet, and etc connected to the driver circuit of the solenoid).
Also, will the solenoid work when it is powered with 6V and 1.5 A?

Link for the solenoid is :https://www.atlas-scientific.com/product_pages/components/solenoid.html

Link for the batteries: Energizer EL123A 3V 1500mAh Lithium – Battery Junction

4444071461462059407.png

The 5volt regulator on the promini (red circle) is toast. And likely more.
Use a new board.

You should have powered the solenoid directly from the battery(+).
A 1.2Amp solenoid is no match for a 5volt/0.1Amp regulator.

The solenoid also must have a (1N4004) diode across.
If you don't add that, then the mosfet will also fry.

Post a hand-drawn diagram before powering it up, so we can check.

How long/often do you power the solenoid.
I doubt that those batteries are the right choice.
Leo..

Hello,

Attached is the figure of my circuit.

Will the solenoid work at 6 V and 1.5 A ?
The maximum power rating is given as 1.2A for the solenoid on the website.

If I add the diode can I use these batteries and power the solenoid?

Thank you!

Diagram seems correct, except for the missing diode.
If you use a PWM output (e.g. pin 5 or 6), then you can PWM (reduce power to) the solenoid once it has activated.
With PWM it's better to use a faster schottky diode (e.g. 1N5817) across the solenoid.
The diode goes across the solenoid, with the cathode (ring) to battery(+).
It does not conduct during normal operation, but kills the reverse kickback spike when the fet turns the solenoid off.

Still not sure if those batteries are able to deliver 1.2Amp long enough.
Leo..

"
If you use a PWM output (e.g. pin 5 or 6), then you can PWM (reduce power to) the solenoid once it has activated. "

If I use the PWM output and the power to the solenoid is reduced , does this mean that the solenoid will receive 1.2A for activating and then once it is activated , if the power is reduced, won't the valve fall(or be in the middle ) ?

can you please suggest any batteries with 5V and 1.2A ?

Also, when I connected the 6V batteries to the solenoid, it switched on and off very rapidly.
What does this mean? Is the current too high for the solenoid ?

Thank you!

PWM turns power to the solenoid on/off rapidly, thus reducing average power to the solenoid.
To the point that holding power is not enough. Up to you to try it.
You might not like it, because you also will hear the whining that goes with it.

You did not answer the time you need this solenoid to be "on".
Those batteries might give in after half an hour or less with that current.

Never a good idea to power sensitive electronics and a motor/solenoid from the same batteries.
You could use four rechargeable NiMh batteries for the solenoid, and the ones you have for the Arduino.
Leo..

The solenoid is being controlled by the arduino which opens for 1~2 sec depending on the pressure signal and the turns off and then turns on again depending on the input pressure signal.
So it turns on and off based on the signal from a sensor.

I used this

The input from the batteries is given to this and the output from this is given to microcontroller.

So when I want to take readings, I switch this on and the power is given to the the components .

Instead of using separate batteries for the solenoid and microcontroller , I want to use the same battery for both of them.
Is there any battery that you might suggest for this ?

*** I used a power supply with 5V and 1.2 A for both the solenoid and microcontroller and it worked fine before.

Only 1-2sec. No need to PWM then.
Use the batteries you have.
Leo..

If so, can you please explain why the regulator was burnt .

Thank you !

dpoornima:
If so, can you please explain why the regulator was burnt.

Don't know. I only know that the kickback of a solenoid when turned off can be hundreds of volts.
You had nothing in place to kill that.
You might have damaged your Arduino the first time, when you turned it off, and cooked it when you turned it on.
And you left out vital information (the power button) from your diagram.
Leo..

Where is the button on your drawing? How is it wired up? Did the regulator burn when you pushed the button (or when the solenoid cycled)? You don't have a flyback diode on the solenoid, so a big power spike was directed right back to the RAW pin when the magnetic field of the solenoid collapses.

Sorry about that. I attached a picture of the button schematic.

The button was not on when this happened. I just connected the vdd and gnd to the button( in and gnd from the battery) and the out and gnd pins to arduino. When I was connecting the pin 4 of the solenoid, the solenoid turned on and off rapidly . I removed the pin 4 and When I was trying to connect to pin 4 again, the voltage regulator gave a spark and the component beside it burnt.

But when I was using the same setup with 5v and 1.2A supply, everything worked fine.

Is it the problem with the batteries am using?

The button was off all this while.
I was to turn the button on after connecting the pin4 of arduino.

It wasn't the battery.

Are you sure you didn't have the battery hooked up backwards? Reverse polarity would have went screaming through the body diodes of the fets of the solenoid module and power switch, causing the solenoid to energize. The regulator probably wouldn't handle it well either.

For future projects, hook the power source up LAST, and triple check polarity. Many modules have reverse polarity protection on them, but many do not. Don't depend on it. It's like wrecking your car to see if the airbags work.

Do I still require a diode then? If the power supply isn't the problem .

dpoornima:
If so, can you please explain why the regulator was burnt .

Thank you !

Maybe due to the known behaviour of inductors (coils) for cases where the inductor has a current through it at one moment, and then the current drops (reduces) at a relatively large rate - such as for a situation when we use a switch to remove current through an inductor (ie. switching off).

Voltage across an inductor is L times di/dt ..... which basically proportional to the rate of change of current. If the current drops relatively quickly, then the rate of change of current can be relatively large. Not only relatively large, but the decrease in current means a negative value for di/dt. So the voltage across the inductor is proportional to a relatively large negative number..... hence a relatively large negative-valued voltage is developed across an inductor during switch-off.

That large voltage could cause a problem for some circuit components - eg... transistors or chip components getting too much energy/heat into them...and becoming destroyed. So methods like placing diodes at appropriate spots in the circuit can help to eliminate the problem.

dpoornima:
Do I still require a diode then?

Yes, always.
Don't know why that module that came with the solenoid didn't have one.
You can use a common $0.10 1N4004, added to the screw terminal block of the solenoid.
Leo..

Wawa:
Yes, always.
Don't know why that module that came with the solenoid didn't have one.
You can use a common $0.10 1N4004, added to the screw terminal block of the solenoid.
Leo..

Absolutely true, and also add some .1uF ceramic disc caps (non-polarized) on the power supply near microcontroller if you are powering it with same batteries. This would further help in reducing the noise.

Thank you for all the suggestions! I will add a diode to the solenoid circuit .

Yes, you will need reasonably fast diode capable of handling 1.2 Amps for a short period of time. Perhaps a Digikey diode "MBRD320T4G" is one of many that will work.

It will be connected across the solenoid. Its function is to limit the reverse voltage of the coil to ~ 1-2 volts keeping it safely in the range of voltages the pro mini can handle.

The one think you should be aware of it the addition of this clamping diode will cause the solenoid go off slower.