TPL-5110 electromagnetic interferences

Other Hardware Motors, Mechanics, Power and CNC
1

Hello guys,

I'm currently working on my degree final project and I have come across with some issues working with the Adafruit TPL-5110 Low Power Timer. My project consists on an automated control system for plant cultivation but I´m having several troubles when trying to work with the water-pump and the TPL-5110.

When the pump is activated it suddenly powers off my TPL and my circuit. I have noticed that it must be due to the EM interferences that the water-pump generates. I tried connecting my circuit with an independent power supply and the pump with another independent power supply just to make sure that they worked well sepparately. As I aproached the water-pump to my TPL it turned it off inmmediately.

I've already shortened the wires as much as possible but I keep having the same trouble.

Anyone knows how to fix this?

2

Then lengthen the wires to the pump so it is further away from the TPL-5110. Since you provide on other documentation, that is all I can suggest!

3

Hello Paul, thank you for your answer. I've already tried that but I keep getting the same issue but with less frecuency (still way too much). Here´s my electric scheme:

electric scheme
electric scheme1090×696 35.1 KB

4

How much startup current does that pump draw.
Those timer boards have a tiny mosfet switch. Sparkfun specs the board at 1.1Amp max.
Leo..

5

Hello Leo, thank you for your answer. I think it should be around 400mA.

6

All motors have a metal frame that must be connected directly to the common ground. In addition, connect small value ceramic capacitors from each motor terminal to the frame of the motor.

7

This is the kind of pump I have, there is no metal frame to connect to ground. Just the positive and negative wires.

8

Cut the plastic away and get to the metal frame! Or better yet, get a pump with a connection to the metal, which will be shielding the brushes that make sparks!

9

But I need this pump to be inmersed in water, if I break the plastic cage I won't be able to use it!

10

Ok, then wind the pair of wires many times through a ferrite core to stop the EMI from getting to the Arduino.

11

Thank you! I'll try it.

12

Don't think. Measure the resistance of the motor with a multimeter, then work out the stall (startup) current with Ohm's law.

But maybe pump current doesn't run over the TPL switch.
Can't follow your diagram, because it's not drawn according conventions and is not annotated.
Leo..

13

You could try to eliminate / reduce the problem by using a snubber circuit. This in effect reduces the rate of rise of current with time. This is what is causing the interference in the first place.

This PDF shows the many ways of doing this, one of these might be your answer.
AN848.pdf (194.0 KB)