Friday, October 27, 2017

Powering your project

In the beginning of this year I was asked to give a demonstration about using electronics in gardening. For this I made a small setup in which I used an ESP8266 (a Wemos D1 mini version) to test soil humidity. As soon as humidity dropped below a certain value a water pump would irrigate the soil.

As a soil humidity tester I just used two wires attached to the analog input of the ESP8266. And I purchased a nice small pump that is nevertheless capable of pumping 80 liter water within an hour. The ESP's datapin is not powerfull enough to run the motor of the pump so I used a TIP120 as a signal amplifier. In theory everything worked as planned. However in reality not exactly.

I was powering all this from the ESP itself. I used a Wemos D1 mini version. The Wemos D1 can be powered by a USB cable and has both 3.3volts and 5 volts output as you can see on the picture. The 5 volts is on the right side and the 3.3 volts on the left side.

Well actually everything did work however the pump was not pumping constantly but it was stuttering. It took me a while to realise that when the pump started working it influenced the reading from the analog port. And that was due to the fact that the voltage regulators on the Wemos D1 mini where not able to supply enough current.

So what to do.
Well the solution is obvious. I needed to power the pump circuit (pump with TIP120) with a separate power supply.

Now I could make a cut in the USB cable and drain some power seperately to my circuit. However there is an easier solution.

At the local dollar store (called Action in the Netherlands) they sell a wall plug with a double USB outlet.

And on my Chinese suppliers site I had bought a few weeks before a micro USB connector for PCB mounting that easily fits on a breadboard.

As you can see this makes life much easier. The only thing is that you need to use 2 usb cables.

An even easier solution was something I found later on the Chinese suppliers website: a USB splitter cable. That is even easier as you will not need to purchase a special wallplug with a double USB connection. I haven't bought one of these yet but I am surely going to.

Just make sure that your wall plug delivers enough Amps to power your circuit. Mines supply 2.1 amps which is more as sufficient for ESP projects.

Till next time.
Have fun.

Luc Volders