Potentiometer gear problems

[iron737]

Hi guys! I'm building a throttle quadrant and for the two throttle levers I'm using two potentiometers (100K) connected with two gear levers like this one (is my prototipe). Obviously I can not use the full range of the potentiometers.

http://s30.postimg.org/6j4k94w6p/20140401_134357_2.jpg

Sometimes it happens that the minimum and maximum values ​​of the leverage change. For example, I calibrate the throttle lever with a minimum value of 500 and a maximum value of 1000 (the values ​​are random), after some use I have a minimum value of 490 and a max value of 990. In this way I can not reach 100% of the engine (of 0% of course) in my flight simulator and I have to recalibrate everything.

What do you think about this problem? The cause may be that the gear "slips" on the potentiometer shaft? How can I fix it?

[iron737]

Connections are ok. I use FSUIPC for calibrate. Unfortunately for me the problem makes it even during a single flight and this is very annoying... during a 30-minutes flight I have to calibrate it 2 times.

[Danilo]

Using FSUIPC check if the value changes if the potentiometer is still for a period of time (let's say 30 min). If the value is constant then the problem is moving, but if the value changed then the problem is electrical.

If the problem arises due to moving then check the connection shaft-gear (is it just friction?) and the backlash of the gear.

If there is an electrical issue check the supply voltage (for potentiometer), is it constant? Where the potentiometer is connected to? Did you try to change the potentiometer?

Regards,
Danilo

[iron737]

Hi Danilo (we have same name ) the value is constant even after hours, so the problem is not electric...to be honest, sometimes (in random way) the value of each potentiometer that I link to my usb card fluctuates rapidly of +/- 1 as you can see in my video here ... but this is another problem and you become my hero if you know how can I fix it

However, as you can see in my photo (first post) the nylon gear is simply "pressed" onto the pot shaft, so I don't know where is the problem in this connection...I think that the nylon gear slips in the shaft but it's just my thought.

[Danilo]

If the issue is mechanical then I would check if the gear really slips. Try to block the shaft with a screwdriver (or tongs) and slowly push the lever. With this test you could also check the backlash of the whole system.

Is it possible that potentiometer reaches its end position during the operation? This is never good when potentiometer is used as position sensor.

I don't know your interface but I think that value fluctuation should not be a problem, since every A/D converter has its limited resolution. Is this the only axis/potentiometer with such behavior? If the answer is yes, I will suspect bad potentiometer.

Good luck,
Danilo

[iron737]

If the issue is mechanical then I would check if the gear really slips. Try to block the shaft with a screwdriver (or tongs) and slowly push the lever. With this test you could also check the backlash of the whole system.

Is it possible that potentiometer reaches its end position during the operation? This is never good when potentiometer is used as position sensor.

I don't know your interface but I think that value fluctuation should not be a problem, since every A/D converter has its limited resolution. Is this the only axis/potentiometer with such behavior? If the answer is yes, I will suspect bad potentiometer.

Good luck,
Danilo

Ok, I tried to block the shaft with a screwdriver and if the lever is pushed the gear slips! Each potentiometer doesn't reach the start or the end position, I configure it to work in the "middle area".

The random jitter problem happens with every potentiometer, so I think that the problem is elsewhere.