Science Buddies: "Ask an Expert"

Does anyone know where I can purchase a 12v peristaltic pump online? I know they have some at Amazon but I don't know if they are reliable since the peristaltic pump is not a seller from the U.S.

Hi sphan-

If you don't want to order from Amazon, the same pump is also available directly from Adafruit Electronics:

https://www.adafruit.com/products/1150

I believe when we listed the pump originally, Adafruit was the Amazon seller, but it looks like that has changed (when I look right now the seller is ZJchao). However, I wouldn't worry about ordering from Amazon. In general if an item is listed as "fulfilled by Amazon" and doesn't have a bunch of one-star reviews from people saying they received a broken or defective product, you should be OK. Do be careful about the shipping time though - sometimes sellers from Asia have very long shipping times, like 6-8 weeks.

-Ben

Thank you Ben your link was very helpful!

If the potentiometer and one of the jumper wires are touching is it dangerous? Will it create a short circuit?

Hi sphan,

Can you clarify what you mean by "if the potentiometer and one of the jumper wires are touching"? Are you building the circuit on a breadboard, as shown in the project's procedure? If you are following our diagrams, then the potentiometer is connected to two jumper wires via holes A25 and A26 as shown in Figure 12:

https://www.sciencebuddies.org/science- ... #procedure

so I'm not sure what you mean by if they're "touching."

Yes I am following the procedure form science buddies. But I just looked closely again and they are not "touching." What I meant by touching was that my jumper wire was connected into hole A26 and my potentiometer is connected into one of the holes B26 right next door to it. So since it was so close together it looked like it was in contact with each since they were so close and I was not sure if it was going to create a short circuit or not.

Hi sphan,

If you have time, I would suggest that you look at our new breadboard tutorial:

https://www.sciencebuddies.org/science- ... d-tutorial

There are a couple things in there that might help you understand better. Two important points:

- The jumper wire and the potentiometer are connected through the holes of the breadboard. This is intentional and not a short circuit. Hole A26 is electrically connected to hole B26 inside the breadboard. The pictures in the sections "What is inside a breadboard?" and "How are the holes connected?" will explain that better.
- While you push the metal pins of the jumper wire and potentiometer down into the breadboard, the parts that remain above the breadboard are plastic. Plastic is an electrical insulator, so even if the parts were bumping into each other, it would not create a short circuit.

However, your intuition that in general circuit parts should not be touching or bumping into each other is good. This can cause a short circuit when two exposed metal parts touch each other. In this case, you are safe since the exposed parts are plastic.

Hope that helps, please reply if you have more questions.