EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: frenky on December 10, 2018, 06:37:54 am

Title: Weird circuit in children toy
Post by: frenky on December 10, 2018, 06:37:54 am
I have bought a bathtub toy which has a water pump in it and it stopped working on the first day.
I thought pump has died so I took it apart to see which model should I order online.
After a month I got it and replaced the faulty one.
But this new pump also was not working so problem was elsewhere.
I took it completly apart and found capacitor in series.
I have never seen that in DC circuit. Any idea why the cap is there?

The whole circuit is battery, capacitor, switch and 5v dc pump in series.
Title: Re: Weird circuit in children toy
Post by: frenky on December 10, 2018, 06:44:36 am
The toy is powered by 3xAA batteries and pump looks like this:
(https://www.xcluma.com/image/cache/catalog/products/BE-01-0977-800x800.JPG)

And toy:

(https://images-na.ssl-images-amazon.com/images/I/616S6Rhdx4L._SY450_.jpg)
Title: Re: Weird circuit in children toy
Post by: David Hess on December 10, 2018, 07:01:32 am
The part is not a capacitor.  It might be a PTC thermister used as a resetable fuse to prevent damage to the battery in the event that the motor seizes.

Title: Re: Weird circuit in children toy
Post by: frenky on December 10, 2018, 08:10:33 am
That makes sense. Perhaps its to low value and its limiting current too much. Because pump was working but it did not produce enough water pressure to spin the accessories.