Science Buddies: "Ask an Expert"

Hello,
While conducting this experiment we are unable to insert the tubes on both ends on the 5V pump and we are trying to use the 12V pump instead which requires an external power supply, how do we connect the power supply to make the circuit work? Is there any specific external power supply that we need to use? Any quick response is appreciated! Thank you!

Hello,

In conducting the experiment on creating an artificial pancreas project, what do we do if both the 5V or 12V doesn’t seem to work? The circuit seems to work as we got the voltage readings for tap water and distilled water but can’t seem to make either of the pumps work. Please help. Thank you.

Hi - a moderator has merged your posts into a single thread so we can reply in one place.

First, you can confirm that your pumps work by connecting them directly to a power supply without the Arduino.

Next, the debugging video in our new Arduino tutorial series might help: https://youtu.be/9GLaU-BCEQM

This is a more complex circuit than what is shown in that video. To figure out what is wrong, you need to isolate the problem. For example, you can write Arduino code that always turns the pump's control pin HIGH using a digitalWrite command, without using an IF statement to check the sensor reading. This will help you confirm that the part of your circuit to control the pump is working (and if you've already tested the pump by connecting it directly to power, you know your pump is working). If the pump then doesn't run when you run the complete code, you may need to change the threshold value for the sensor.

As for which pump to use - as far as we know, the tubing that comes with the 5V pump should connect to it. If you bought the pump from Adafruit (as linked in our project) you could contact them for support.

If you decide to use the 12V pump, you also need to check the current requirements, which are listed as 200-300mA on this page: https://www.adafruit.com/product/1150. So for example, this adapter from Adafruit provides 1,000mA which would be more than enough: https://www.adafruit.com/product/798. However, to connect it to a breadboard, you would either need to cut off the barrel plug, or purchase an adapter like this: https://www.sparkfun.com/products/10288

Hope that helps!

Ben