Who wants to add a cheap USB air pump to a hydroponics system or aquarium? This USB air pump (USB Air Pump Amazon Link) comes with a USB cable, air stone, air pump, and air tube. This can be used in the current hydroponics system which is growing Basil indoor.
Commercial Air Pump for Hydroponics
Good things about USB Air pump are
- A lot of air pumps can be powered at 12V. USB power offers a 5V option.
- The air pump can be portable with a USB charger
- Small form factor
The price is currently at $14.99 from Amazon.com on May 25, 2020.
USB Air Pump Tear-down
First, I opened up the rubber cover and noticed that there was a relatively big resistor between two terminals of the air pump.
This is still a bit old technology here 🙂
As you may know, this is a USB power device. With the multimeter, the voltage across the air pump is just what a USB cable can supply, which is 5V.
What’s the resistor value?
Then, I measured the resistor value. According to the resistor cheatsheet (it has been so long since I checked this cheatsheet last time 😛 ), it is 51 Ohm.
After that, I measured the resistance across the air pump when the USB power is off. Then, the resistance value was recorded at 7.7 Ohm. So, there is some parallel resistance coming from the air pump.
Then, instead of the USB power, I used a lab power supply to power this air pump. At 5V, there is a current flow of 0.24A (240mA).
This means that Arduino digital output pin (~60mA) cannot power this air pump. So, we need to use an Arduino 5V supply or external supply. Ouch!!!
On the right side of the current hydroponics picture below, there are a USB powered air pump and USB charger, so this can be a portable hydroponics system.