Help with Water Pump

[salty joe]

YES! The trip test worked with the pump. Thank you very much. Later on I might have a Schlitz or a PBR. I still like the cheap beer I grew up on

But when I connected the logic circuit (hopefully that's the right term) the pump only ran for the first toggle so I set the trimmer at max and still the pump only ran for one toggle.

 

[4pyros]

Still following, dont give up Salty!!!

 

[KeepItSimpleStupid]

I'm still here and I think for the most part I'll let Alec lead and I may have the wrong idea of the circuit operation in my head.

@Alec
You might try simulating while include the actual driving device or similar part. Having different behavior when the timer is attached is suspicious.
e.g. If the input was driven by a 7404 inverter (it isn't) include that in the simulation. Remember fan out.

 

[alec_t]

YES! The trip test worked with the pump.

Good. I think we can say the PDM is now working as intended.

But when I connected the logic circuit (hopefully that's the right term) the pump only ran for the first toggle

What sort of toggle period are we talking about?

so I set the trimmer at max and still the pump only ran for one toggle.

Now that we've established the pump will run with the trimmer at min it would give better protection for the pump to leave the trimmer at min for future runs.

@KISS
Good point.

You might try simulating while include the actual driving device

Yes, I'll do that.

 

[salty joe]

Thanks all.
The toggle is set at about 5 sec. off, 14 sec on.

With no load, the V coming out of the driver is 21.2V on every toggle.
The first toggle with the pump running shows 17.1V at the jack. Every subsequent toggle with the pump hooked up but not running shows 20.2V at the jack.

This is not exactly good news, is it?

 

[alec_t]

I'm not sure I understand your set-up.
Can you confirm you have disconnected the constant 12V from the PDM_Mk10 control input (left end of R1) and that now:-
1) From the tidal timer module you are geting 12V for the PDM logic supply voltage (+12),
2) From the tidal timer module you are geting a 0/12V control signal toggling at 5s on / 14 s off which is applied as the +Vt signal to the control input (left end of R1) of the PDM,
3) The 'V coming out of the driver' is the voltage at the 'Pump-' terminal of the PDM,
4) 'at the jack' means at the 'Pump-' terminal of the PDM.

I assume your tidal timer module version is the one I posted in June, namely
View attachment 67900

 

[salty joe]

Yes, I disconnected the constant 12V from R1.
1) From the tidal timer I do get constant 12V (11.8) for the PDM 12V.
2) From the tidal timer I do get 12V (11.8) for 14 sec and 0V for 5 sec and it is connected to R1.
3) yes
4) yes
No, this one from May, post 367. **broken link removed**

I did not use the driver part and added voltage regulator and caps for the 12V.
Thank you for looking at this, Alec.

 

[alec_t]

I did not use the driver part

I take that to mean the +Vt signal for the PDM_Mk10 is taken directly from the output of U3c/U3d in that version, and that components shown to the right of U3c/U3d are disconnected or non-existent?

 

[salty joe]

Yes, everything shown to the right of U3c/U3d doesn't exist.

U3c is fed to R1 of the PDM. For tide simulation, there are two PDMs on one board and the left side of both R1s are connected together.
U3d is fed to another pair of PDMs.

Thanks Alec

 

[salty joe]

Sorry-double post-my computer does squirrely things when the McCaffee is running a scan.

 

[ronv]

Did the alarm sound when it was time for the second cycle?

 

[salty joe]

No, the led just kept toggling along. The pump will only run for the initial toggle.
I'm gonna try another pump.

 

[ronv]

Interesting. The pump and LED have the same voltage across them. Perhaps the voltage is high enough to light the LED but not to start the pump the second time. Maybe you could measure the voltage across the pump.

 

[salty joe]

I plugged in a different pump and it is working as it's supposed to! It has been toggling on and off for the last 10 minutes or so.

 

[ronv]

I'd try it again with the one that only ran once and measure the voltage. There are a lot of variables in the circuit so you wouldn't want to be sorting thru pumps to find some that run.

 

[salty joe]

I'd try it again with the one that only ran once and measure the voltage. There are a lot of variables in the circuit so you wouldn't want to be sorting thru pumps to find some that run.

The first toggle with the pump running shows 17.1V at the jack. Every subsequent toggle with the pump hooked up but not running shows 20.2V at the jack.

I tried a third pump and it would not run at all-it put the driver into alarm mode. If this thing comes down to crappy pumps...well what a waste of brilliant schematics. I hope the balky pumps can be made to work.

 

[ronv]

I'm thinking the other side of the jack is the power supply at 20.2 volts so that says the pump only has 3.1 volts across it--probably not enough for all of them to start. The voltage is low most likely because the circuit is in current limit. If this is the case there may be a point that the circuit is in current limit but has not tripped U1d to sound the alarm. We can check that later. If you have another 0.22 ohm resistor add it in parallel with the one that is there. This should raise the current limit.

 

[KeepItSimpleStupid]

I tried a third pump and it would not run at all-it put the driver into alarm mode. If this thing comes down to crappy pumps...well what a waste of brilliant schematics. I hope the balky pumps can be made to work.

We sort of knew this from the start. I still haven't been able to contact Melixis. Tried 2x by email and 2x by phone.

Don't give up yet!

Something you might do, is take just the power supply brick and the 0.22 resistor in series and measure the voltage across the 0.22 resistor and the voltage across each of the motors. It could give us an idea of the variation in the motors. Mark the motors and the resistor you used for reference. This would give us an idea of the motor variation.

Without another voltmeter we can't determine the absolute accuracy of the 0.22 resistor. Probably no big deal.

Tolerences can create havoc in a design, moreso if you don't know what they are.

Remember the resistor? It is a known load. As the motors pick up goop from running, the bearing friction is going to get larger. This will eventually cause the motor modules to trip and that is a good thing. It's also why I wanted you to to easily be able to measure the voltage across the sense resistor.

We/I started with if it's impossible to make these motors work, lets dissect them (we did) and make something that will. I really don't want to go there though.

 

[alec_t]

Whoa! Hang on guys!
At power on the counter in the tidal timer module resets so that U3d is the 'active' output and U3c is the 'inactive' one. The PDM under test should therefore be connected to U3d for a toggle test, but as per post #1089 Joe has it connected to U3c. That means the pump is only being pulsed in 'flick' mode. So it's not surprising it won't run continuously and may account for the odd voltage measurements at Pump-.
I think we're jumping the gun here. IIRC we had a problem with the second PDM on the same board as the PDM we've been testing to date. It would be better IMO to resolve that problem before trying to toggle the pump, in case the problem has some interaction with the first PDM.
I'd suggest reverting to the test set-up with a constant 12V at the +Vt input of the two PDMs and a bulb as dummy load for both. Then compare voltages at similar points in both PDMs to locate any discrepancy.

 

[salty joe]

I used the "active" or toggling output for all pump testing. I used a SPDT to switch over if I get flick mode. I have only tested one pump at a time. Oddly, when the pump that toggled and ran the way it's supposed to, the run time (toggle time) decreased from about 14 sec. to about 11 sec.

I have used drivers from both boards. I do have the drivers labaled A-D for the tide and 1, 2 for the wave. When we get back from our annual Oct. camping trip on Sun., I'll label the pumps, run 12V back into R1 and start taking notes.

Can't do anything now-I have a boatload of tasks before I go to work.

Thanks a ton one and all!