Help with Water Pump

[salty joe]

[QUOTE @Joe
A few further thoughts:

For safety the pumps should have individual manual 'off' switches.

As you're new to electronics construction may I offer a few suggestions?
1) Google for tutorials/demos on soldering techniques.
2) For point-to-point wiring on the circuit board you will need hook-up wire. Solid core is best (to avoid odd strands which might cause shorts), e.g. old telephone cable. The only wires carrying significant current are those from the FETs to the pumps, for which flex may be preferable.
3) Use fine flux-cored solder (not plumbers' solder!). 60/40 leaded solder is much easier to use than lead-free (but be aware of health concerns).
4) Practice soldering on a scavenged circuit board (old TV etc, which might also be a source of hook-up wire).
5) The circuit is modular, so build a one-pump module first to check its operation on the bench, using a mains filament light bulb as a dummy load in place of the pump.
6) Apart from the pots, C3 and C5 the components are polarity-sensitive. Make sure to identify correctly the polarities and pinouts (from datasheets as necessary). Remember that the underside view of the board is a mirror image of the top side; it's easy to get confused with pin numbering!
7) Take anti-static precautions when handling the IC and FETs.
8) Don't be surprised if the circuit doesn't do what it's designed to do when you first power it up. We've all been there, done that! Provided you have a multimeter we can sort out any problem. Common problems are a missed or wrong connection, or a solder blob shorting two copper tracks.

Good luck with the build. Keep us posted on progress.[/QUOTE]

The pumps have a cord that is 2 meters or so long with a special round connector into the controller. I would hate to cut that cord to install a manual switch. Is there a better way?

1. Found a really good video on U tube.
2. check.
3. check.
4. Found an old TV & practiced soldering, I think I'll be OK there.
5. Would a 40w incandesant bulb work for a dummy, or would I need a flashlight bulb?
6. Will do.
7. OK.
8. Thank you.

 

[alec_t]

5. Would a 40w incandesant bulb work for a dummy, or would I need a flashlight bulb?

Fine.

I would hate to cut that cord to install a manual switch. Is there a better way?

Won't you have to cut the cord to connect to this new circuit? The alternative is to find a mating connector. Is it a common type?

 

[salty joe]

I was going to salvage the female connector for the pump from the controllers that were supplied with the pumps.

For safety are you thinking safety for the operator, safety for the tank inhabitants or safety for the pumps? I thought that because this will be 24v at fairly low amperage, even a bad short that somehow was missed by the GFI would not be a big deal. Am I wrong?

 

[alec_t]

I was thinking more mechanical safety, if there's any prospect of someone/something getting trapped/hit by a pump moving part. But I think even 24V could be harmful to tank occupants (human or otherwise). A GFI seems essential; glad you've got that.
Could you fit individual pump switches between the female connectors and new controller?

Edit: BTW, if the 40W bulb is mains-rated then it obviously won't glow brightly with a 28V supply, but it should show if things are working.

 

[salty joe]

If I ever came home and found something stuck in a pump or some crazy thing happening, I could unplug the four pumps and then plug them in one at a time to find the problem pump. Or I'd probably unplug the controller and go trom there.

 

[salty joe]

The electronic parts came in. The leads on the Schotky diode 1N5822 (replaced MBRS340) are a little teeny bit greater diameter than the holes in the proto board. Should I drill the board or get different diodes? Also, the pots have three hookup tabs. Is there a plug for them or do I solder hookup wire to the tabs?
I expect the power supply any day.

 

[alec_t]

How teeny is teeny? If the protoboard has copper pads/tracks and drilling would still leave enough copper to give a good solder joint then drill. If not, you could use hookup wire between diode and board, perhaps gluing/Blutak-ing the diode to the board for physical support. A similar method for the pots, too.

 

[4pyros]

Should I drill the board or get different diodes?

You will most likely have to use the ones you have, most diodes will have bigger leads for heat disapashoin. some times you can just ream the holes out some with a small pick, it is less likely to damage the board then drilling.

Also, the pots have three hookup tabs. Is there a plug for them or do I solder hookup wire to the tabs?

If thay are board mount I would solder scrap leads to the tabs and solder that to the board.

 

[salty joe]

By a teeny bit I mean the diode lead will almost go through the hole. I'll gently open the hole a bit.

I took a few minutes to check out these parts and am not sure about the polarity of the capacitors. One lead is shorter and there is a grey stripe on the side of the capacitor with the shorter lead. Inside the grey stripe is a narrow rectangle. No + or - to be found. Is that normal?
https://www.taydaelectronics.com/catalogsearch/result/?q=a-4534

Also, the FET and voltage regulator were not marked at all other than fine print identifying the part. I went over these parts with a magnifying glass and a bright light. They both have three leads and the schematic shows three connections, but I can't figure out how these two parts should be hooked up.


https://www.taydaelectronics.com/catalogsearch/result/?q=l7812cv

https://www.taydaelectronics.com/catalogsearch/result/?q=irf3205

 

[4pyros]

Inside the grey stripe is a narrow rectangle.

That is negative.
You will need to look up the data sheets for the other parts to get the pin orientation.

 

[salty joe]

OK, thanks.

 

[salty joe]

On the 7812 regulator, pin 1 is input, pin 2 is ground and pin 3 is output. I can't figure out which pins go where.

I look at the schematic from post 99 and the middle wire connects to ground with no capacitors in between. Assuming the arrow pointing down at the far bottom left is ground. So I'm thinking the middle wire should go to pin 2. The wire to the left is 24v and the wire to the right is 12v, so does the wire to the left go to pin 1 and the wire on the right go to pin 3?

Alec, any chance you could send me a PM? I have a non electronics question for you.

 

[4pyros]

The wire to the left is 24v input pin 1.
The middle wire connects to ground yes pin 2, the tab with the mounting hole is also connected to pin 2.
The wire to the right is 12v output pin 3.

 

[salty joe]

Sometimes I make lucky guesses.

With the IRF3205 (replaced IRFH5207) the tab and pin 2 are both drain. They are connected internally so it is my impression that I only need to connect pin 2 to drain and forget the tab other than making sure nothing touches it.

Am I safe to assume the same with the 7812 and connect pin 2 to ground and disregard the tab?

 

[alec_t]

With the IRF3205 (replaced IRFH5207) the tab and pin 2 are both drain. They are connected internally so it is my impression that I only need to connect pin 2 to drain and forget the tab other than making sure nothing touches it.

Am I safe to assume the same with the 7812 and connect pin 2 to ground and disregard the tab?

Correct on both counts. The tabs are for connecting to heatsinks (which aren't necessary in this project). I'll PM you.

 

[salty joe]

I'm putting components on the proto board to get a feel for this kind of work and to see how it will fit. I'm starting with the timer supply. C5 connects to the negative side of C4 which connects to the ground of 7812. Would you solder a wire to one side of C5 and solder the other end to the negative side of C4 along with a wire to connect to the ground of 7812? So there would be two wires soldered to the negative side of C4, one going to C5 and the other to 7812. Or, is the proper technique to make junctions in the wire and make it look like the schematic looks. Not sure if the schematic is drawn like that for the sake of clarity and the actual hookup is a little different.

 

[alec_t]

From what you're saying it seems your protoboard is of the type which has copper pads, not tracks?

So there would be two wires soldered to the negative side of C4, one going to C5 and the other to 7812.

That's fine. No need to make it look like the schematic physically; the important thing is that the electrical continuity between components is correct. Schematics are generally drawn with all components on a regular grid. Just look at that old TV panel and you'll see that practical circuits don't stick to a grid!

Edit: For a conductor, such as the Ground line, which has a lot of components connected to it you may find it easier to use a length of bare hookup wire between two end points as the ground and solder the component leads to that at intermediate positions. So it would in that case resemble the schematic.

 

[salty joe]

Thanks Alec, yes the board I have has copper pads. Before I start soldering tommorrow, could I get a confirmation on the MOSFET hookup? The way I see it the connections are in a verticle column with the top being drain, the middle being gate and the bottom being source-is that right?

Also, I am having a hard time finding a datasheet for the pots. Can anyone point me in the right direction so I can figure out how to connect the pots?

The power supply should arrive any day.

 

[4pyros]

Also, I am having a hard time finding a datasheet for the pots. Can anyone point me in the right direction so I can figure out how to connect the pots?

The center tab is the wiper the moving part or the lead with the arrow on schematic. The outside tabs are the ends of the resister and can be hooked up ether way.

 

[alec_t]

The way I see it the connections are in a verticle column with the top being drain, the middle being gate and the bottom being source-is that right?

Correct. As 4pyros says, it doesn't matter which way round you connect the two 'outside' tabs of the pot (I'm assuming the three tabs are in a line; not in a triangular arrangement). Which way round you connect them will, however, determine whether you need to rotate the wiper clockwise or anti-clockwise ( if the pot has a rotary control) to increase the pump 'on' or 'off' time.