Power drop out

Hi.
I am working on a arduino based project where I get short power drop outs when there are 2 large AC motors spinning up. What would be ideal for short (1-3 second) power source alternative for arduino?
Large capacitor? What circuit would I need?
It`s an arduino nano which draws around 50mA with all its bits connected.

show us the electrical circuit.

Sounds like a large load is depressing the supply to the arduino

Perhaps battery backup. The Nano from the description appears to allow both 5V in on pin 27,
and on USB, and takes power from the higher voltage of the two. So perhaps a 4.5V or 3.7V
battery supply to the 5V pin might be a way. Also copes with longer outages of course.

You might also find that a larger USB supply (such as a 2A one) would store energy for longer
and ride out the outage (ie its worth trying if you have one to hand, there's no guarantee it
will help).

A capacitor would have to be very high value to help bolster the 5V for several seconds, alas.

MarkT:
So perhaps a 4.5V or 3.7V battery supply to the 5V pin might be a way.

So u suggest connecting say 700mAh 3.7V LiPo to arduino ground and positive to one of the arduinos digital pins? How would the battery get charged?

Here is a link what my current circuit looks like.

MarkT:
Perhaps battery backup.

Definitely.
If only as a test.

Power the arduino from a battery to identify the problem.

Why do you show 240VAC at the input end and a 110v wall-wart and 110v motor?? Typically, those little wall-wart supplies only have just enough capacitance to filter the supply .... sort of. A larger filter cap on the output of the wall-wart would definitely help. You don't indicate if the wall-wart is a linear or switching type supply.

  1. Connecting directly to IO pins anything less than 4.2V does not help.
  2. As for the psu it is a mobile phone charger so I suspect it is of a switching type.

So something like this would work fine connected to vcc if I get 12v psu and a 10V regulator?
Right guys? :slight_smile:

Hi, guys. Me again. :slight_smile:
Just wondering if I could connect a 3x5.5V 4.0F super capacitors in series for short dropouts(~100-500ms) on 12V DC power supply
(circuit current draw ~1.2A @ ~12V DC)?
Thanks

Did you try the suggested battery supply for the arduino ?

You have a circuit connected to the mains supply with probably a common earth.

Strange things can happen with mains earth and 5V logic circuits.

I am working on a arduino based project where I get short power drop outs when there are 2 large AC motors spinning up. What would be ideal for short (1-3 second) power source alternative for arduino?

Your diagram shows one 1200W motor. If you have 2 of them, that's 2400W motor load connected to one 1500VA transformer, then it is under sized and there'll be considerable voltage drop on startup.

In any case (one or 2 AC motors), it would be much better to use a DC supply that's rated for and connected to 240VAC mains instead of the transformer's 110VAC secondary. This will prevent the adapter from seeing the transformer's primary-secondary drop during startup and also when the motor(s) are subjected to load.

P.S. Your diagram shows a relay that has 12VDC marked on it. Make sure it has the proper driver circuit and voltage supply for the relay's coil.

dainazinas:

  1. Connecting directly to IO pins anything less than 4.2V does not help.
  2. As for the psu it is a mobile phone charger so I suspect it is of a switching type.

So something like this would work fine connected to vcc if I get 12v psu and a 10V regulator?
Right guys? :slight_smile:

There are several problems with the circuit you show - you indicate the draw is 1.2A, but the 7812 is only rated 1 amp if I remember correctly. Another issue, you can't keep the 12v battery charged that way - if it is a standard lead-acid battery, the normal charge voltage is about 13.7v - you have 12v - 0.7 volts (diode drop) so the best you could get is 11.3v which will not charge the battery at all.

The mobile phone chargers I have looked at just used capacitive reactance to drop the line to a working voltage for the charger and not a switching type regulator (which is why they tend to have issues when running off an inverter which has a square wave instead of a sine wave - a square wave is essentially a much higher frequency than the line frequency lowering the capacitive reactance and causing heating).

1200W a/c motor could be anything, shaded pole induction, universal, synchronous....

Please give full details of the motor and transformer - induction motors in particular
take more current(*) than their power rating would suggest due to being inductive. This
could burn out your transformer.

(*) At start up and stall it can be many times more than normal running too.
Do the motors should have a plate with the electrical details? If so a legible photo of it would
be good to see.