FP PWM Valve

[Old Grey]

Anybody want to hazard a guess as to what's inside the old Flow Performance PWM Valve FV3.

http://www.flowperformance.com/pwmvalve.html

When I bought my 2007 FP1 I had the PWM option fitted, and since I don't have the money to buy the PWM, I could probably make it for next to nothing if it's simple.

I'm betting it's just a small geared DC motor with some simple transistors, because it has an internal 9 volt battery and the connection coming out of the FP1 is a simple 1/8 audio jack - 2 pole -.

If it's easy to do I will have a go, but I'm not too fussed about doing a simple manual operated thingo because this bench is quickly becoming a slap-together project until I get a sponsor to build a serious PTS bench.

[Brucepts]

RC Servo motor attached to a shaft and a butterfly valve in a PVC pipe

I do not know anyone who has it working though . . . Racehead (George) here on the forum was selling his a few years ago, probalby still has it forsale

[Hotz]

Our viewing this information I realize how Bruce PTS evolved.
Amen guys .. PTS diy ...
PTS today worldwide.
I can not imagine doing all the calculations to get the results, temperature change etc..
PTS system digital is better in every apectos with low price ...
I have many miles internet and found nothing so good easy to use and do ...

[Old Grey]

RC Servo motor attached to a shaft and a butterfly valve in a PVC pipe

The FP1 only has 2 wires through the audio jack, where as RC Servo has 3 - I will have to do more research into how they work -, but either way I don't think I can get a RC servo cheap so I will probably stick with manual - it would have been interesting, but on the other hand I have seen the SF1020 hold a fixed depression -.

Our viewing this information I realize how Bruce PTS evolved.
Amen guys .. PTS diy ...
PTS today worldwide.
I can not imagine doing all the calculations to get the results, temperature change etc..
PTS system digital is better in every apectos with low price ...
I have many miles internet and found nothing so good easy to use and do ...

Yeah I know, I got lumped with a $1000 boat anchor because my timing was out

[Brucepts]

The FP product uses a RC Servo motor. I truly know it does

[Old Grey]

The FP product uses a RC Servo motor. I truly know it does

Now that I have read a bit about how a RC servo works - I only did my first stepper earlier this year -, it makes more sense. Of the 3 wires, 2 are + & -, which accounts for the battery, and the other is for input pluses - I suppose the audio jack has 1 wire for pluses and 1 as common ground -.

If I see an RC toy at a junk sale I might think about it.

[Brucepts]

The FP products use a battery as they are "liability lawsuit happy" and are afraid someone will burn something up with a low voltage wall transformer.

[Brucepts]

Futaba FP S-28 servo to be exact . . .

Servo circuit uses the same pressure sensor as the static reading and they can not both use the sensor at the same time so one has to wait on the other.

[Tony]

Servos have really advanced hugely over the last twenty years.
When I was a kid, there were no radio controlled toys, no micropreocessors.

These radio control model servos are now everywhere, dirt cheap, and the Japanese digital ones are using closed loop microprocessor control for incredible speed, output torque, and precision of movement.
The motors are usually the three phase synchronous type, using a rare earth magnet rotor with very low inertia, and very high rpm capability. Just like a mini variable frequency drive.

Earlier (now obsolete) dc servos used a dc motor and a gearbox with an analog voltage input.
Drive by wire throttle servos are still like this.
Even stepper motors are obsolete for model applications, much too slow and very poor power to weight ratio.

The industry standard now seems to be three wires with a 4.5 volt battery (plus and minus), and the third wire being a digital input of 50 Hz pulse width modulated from zero to 100% for the full range of movement.

The reason for this, is the radio receiver just spits out a continuous serial data bit stream, and the signal to each individual servo stays digital. This is all a very easy job for a low end microcontroller to steer the right pulses to the right servo.

To use one of these servos you need to generate a 50 hz pulse width modulated signal to feed into it.
Not that difficult to do, but a bit of a nuisance.
The dynamic performance, physical size, and accuracy of one of these $30.00 Japanese digital servos will astound you.