Repairing a tabletop waterfall/fountain - Page 1
Forum section: electronics / repair

author: TrmickCO
author_rank: Newbie
timestamp: January 18, 2018, 03:56:10 am
content: Hello. I was hoping to get some advice on repairing (rebuilding actually) the circuit for one of those tabletop waterfall/fountains. I've attached a couple of photos. One is what I'm thinking is a piezo disc sensor. I'm guessing it is there to determine if it's low on water so as not to damage the pump maybe?? That photo is attached. The other is a crude schematic (I'm still learning) which I drew by looking at the original board. There is a mystery blob chip with six pins. With some help, someone suggested it is simply an op amp. I have limited knowledge with those and don't see many 6pin ones on places like Digikey etc. Some I'm wondering what you might think the chip is, if the disc is a piezo sensor, and if the circuit looks like it might work? Sorry for all the questions! Any input is much appreciated!

author: helius
author_rank: Super Contributor
timestamp: January 18, 2018, 04:07:46 am
content: The correct way to draw such a diagram is with the inputs (in this case, the battery voltage source) on the left side, without a ground net unless it is required to prevent overlaps. The C2 is in parallel with the battery, so it should be shown that way.The negative supply rail should only be drawn on the bottom, not as a ring around the circuit as you have done. Likewise, the positive supply rail always stays at the top.The outputs go on the right side: the motor is low side switched, so it is drawn between the top positive rail, and the output of the driving transistor. Transistors are always drawn with their high side on top and low side on the bottom (for NPN transistors, the emitter points out and is on the bottom). It is standard to draw transistors with their base on the left side because that is the input.

author: drussell
author_rank: Super Contributor
timestamp: January 18, 2018, 05:29:22 am
content: If it has some kind of piezo element, I would expect it to be some kind of ultrasonic transducer to make mist.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 18, 2018, 05:49:31 am
content: It looks like it's intended to be a built in "clapper" so the pump only runs on demand. As in clap to turn it on.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: January 19, 2018, 03:42:37 am
content: What does this device do? Left me utterly baffled!

author: Gregg
author_rank: Super Contributor
timestamp: January 19, 2018, 04:34:32 am
content: I think the disk may be a pressure switch (very low pressure on the opening may toggle a diaphragm that in turn operates contacts). If it uses a microswitch you may be able to hear it click if you blow gently into the opening; or connect an ohm meter to the output and try gentle pressure. It would stand to reason the pump would shut off if the water level wasn’t sufficient; pump seals die quickly when run dry and a cheap pressure switch is less costly than a magnetically driven sealed pump.

author: TrmickCO
author_rank: Newbie
timestamp: January 22, 2018, 11:09:44 pm
content: Thank you helius. As I said, my experience in drawing schematics is somewhat limited. I appreciate the input, and will take the tips to heart hopefully in the next project, or fiasco, debacle I'm involved in

author: TrmickCO
author_rank: Newbie
timestamp: January 22, 2018, 11:16:21 pm
content: Hey NiHao. Thanks for the idea. I wondered myself. Owner says it simply worked like: turn switch on, water is gently flowing. No sound, no mist, no nothing. That's why I was leaning toward the piezoelectric being for water level detection.

author: TrmickCO
author_rank: Newbie
timestamp: January 22, 2018, 11:21:27 pm
content: Hello Neo... Simply type into a search something like "indoor decorative water fountain/display". This is the board from one of those. I wonder though, any input from anyone on whether my crude schematic would run? Even if we toss out the mystery blob chip and the piezoelectric and just get an opamp in there? All it has to do is when turned on, water flows and the universe is happy again :/

author: james_s
author_rank: Super Contributor
timestamp: January 22, 2018, 11:52:00 pm
content: I'm assuming the thing did work at some point? If so, how did it behave?

author: TrmickCO
author_rank: Newbie
timestamp: January 28, 2018, 11:06:08 pm
content: I'm not the owner, but I'm told you just switch it on and the water flows/circulates. One day just quit. Nothing beyond that. I had to do a fair bit of destruction to get in, why I decided to just build a new replica circuit ,(parts are around), and put my own little cheap pump in...So, my poor schematic drawing is exactly what I see. My original questions were if someone knew the purpose of that piezoelectric disc (I think water level) and what the mystery chip is. I'm leaning toward opamp....At the end of the day I really don't necessarily need that exact circuit. I just need to power a little pump with AA's to get the flow of water, and semi decent efficiency.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2018, 07:15:32 am
content: It must not have run continuously if it ran off AA's, that wouldn't last long at all. I'm starting to think it is a sound activated circuit that runs the pump for a few minutes when triggered by a noise.

author: TrmickCO
author_rank: Newbie
timestamp: January 30, 2018, 03:56:12 am
content: Correct. Typically they are switched on every now and then for ambience, relaxation, reading a book or the like. You can find them in many garden centers etc. of typical outlets. Some pretty cool, creative designs out there. I mean artistically speaking. The circuitry often is given less attention and arranged for no user access (unless you're hard headed like me) and when they don't work anymore, people just trash the whole thing. Anyways, I'm told no sound or sound activation. I'm just going to build a simple circuit to power the pump when switched on. I don't have the knowledge with those piezo elements to even understand its purpose aside from detecting water level possibly.