TPH-055 Pump Controller

[Chad Ramey]

I took a look at the "Turbo Pump Theory" post and saw that there was quite abit of discussion about these little pumps that were cheap and plentiful off of ebay a few weeks ago. I thought I'd throw in my opinions/troubles on the pumps so far. (Before I start throwing all of this out there, I'll mention that in past experiences, electronics have proved to be quite an enemy to me, and my knowledge is severely lack. Please forgive my noob-ness and if you have any suggestions/criticism, I'd greatly appreciate it)

So, I ended up snatching one of the pumps for $80 bucks off of ebay and it arrived with tons of gunk on the outside of it. After cleaning the outside, I took a look at the blades and the seemed to be clean and spin freely. Upon seeing Alex's post on the fusor.net (http://www.fusor.net/board/view.php?bn= ... 1283393372) forum with a controller schematic for the thing, I ordered all of the parts required for constructing the circuit. Over the past two days, I've manage to build the controller on a piece of breadboard (just like the picture).

I got around to testing it this afternoon (in air), and it has landed me in a state of confusion. Every time 24-28 volts is applied to pinA on the pump, the blades seem to make about a full rotation and then proceed to slow down and stop. The red light shines constantly and the green light has made no appearance. I wouldn't be surprised if the fault was to be found in the circuit that I built but I've checked it a 'coupla times and saw no fault (other than the fact that it looks like a mess). I here is a picture, who knows, there may be something I'm missing. (http://www.flickr.com/photos/chadramey/5015568233/)

Anyways:
Should I be concerned that the pump itself is faulty?
Should 24 volts run the motor (for test purposes)?
Is there a simpler circuit I should try building?
Need any more info?


Thanks,
Chad

[johnf]

Chad
is that the 10 ohm resistor lower left in your photo if it is connected to the supply rail that also feeds the 7400 etc that rail has to be 5 volts

the original circuit on fusor net had the resistor fed from +28 volts to the motor windings common terminal the logic stuff runs from +5 volts and both the +5 volt and +28 volt supplies negatives are tied together

[Chad Ramey]

John,

The 10 Ohm resistor is located on completely separate rails than all of the digital logic stuff.
But of the grounds from the +28 and the +5 are tied together.

(perhaps this is of worth: For the +5 volt supply, I am using a nine volt battery with a +5 volt regulator and just used the negative side of the battery as ground. It sounded like the right thing to do at the time. Is that the correct setup for this circuit?)

[Doug Coulter]

Thanks John. When they are that dead, it's usually something like that.

Chad, did you get that scope working? You're going to need it to do much of anything serious that varies vs time, which what this is all about.
A further suggestion would be to disconnect the driver outputs from the pump windings and substitute some pullup resistors to the 24v supply, and look at what comes out
when you twirl the rotor (in various places in the circuit). Does the hall sensor flip as the rotor turns? Is there a slow, low volt sine on the motor windings when you turn the rotor?

Divide and conquer is the basic strategy of troubleshooting -- after you understand how a circuit is supposed to do what you want it to do.

So get the data sheets, and try to understand how that one is supposed to work, or at least what it's supposed to do with the inputs it gets.
(full understanding of how that interacts with the pump inputs and outputs and time delays can come once you get it to run a little, it'll be easier then)

And check those inputs, the right power to the right places, the trigger from the hall sensor, does the timer run when it's supposed to, and all that.
And, of course, ground where it belongs.

The scope will tell all that if used to advantage. At some point, you'll be finding that you can hook the H trigger and V input together, get a good picture on a
signal with triggering setup right, then move just the vert input to somewhere else and see all time differences from the original trigger...not as good as having
a lot of vert channels sometimes, but it's a worthy dodge when working on the cheap. Get that working first, the rest will be easier then.

[Chad Ramey]

I tried to measure the frequency output with a meter today, but never managed to figure out which pin (or if the pump itself) is ground.

Another quick thought that came to mind: We noticed today that the schematic doesn't address pins D and H. Am I also missing something there? I'll head to the scope (I have access to one at school [I haven't been able to locate any probes for the tectronix scope yet]) and the books tomorrow to get a better look into things.

Based on the +5v supply I described above; do I need to change anything with it?

Thanks,
Chad

[johnf]

Chad
As long as if you have put the required caps each side of the 5 volt regulator ie close this should be fine ---pp9's cost heaps so you should be planning to get rid of them

get to the scope and if you are not sure get someone that knows to help