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1  Using Arduino / General Electronics / Re: Small potentiometer range to give full 0-5V? on: January 29, 2013, 11:26:20 am
@Grumpy_Mike: I thought I was quite clear in my initial post that I am using a pot with analogue input. I have years of experience working with encoders to know that it would not suit this application so I did not even consider it. You are right about the op amps though, and I have scrapped that idea.

@Lefty: Yes, this is one of my ideas. I was thinking using R/C servo linkages. Even if it would only give me just under 180degrees of travel on a pot. Problem I got with it is that it might mechanical lockup if you go over the 180 degrees and I might not have the space for this. I have not ruled out this idea either.

@fungus:This is the current idea I am entertaining right now. You get these plastic experimental/educational kits with gears to play with. One I want to try is a straight rail gear which turns a round gear on the pot when the pedal is depressed. Then there are also the toy and R/C electric motor gearboxes. That might also work. Thanks.
2  Using Arduino / General Electronics / Re: Small potentiometer range to give full 0-5V? on: January 29, 2013, 05:19:46 am
Your original figures give you quite a bit of precision (1 in 152). Is that not enough?
Consider that this is a forward backward control with center off, so in fact I have then only 0-76 each way.
Then, I set some dead band around the center, reducing it even more.
I also have a quick calibrate function for the maximum ends where I store the center point and maximums in EEPROM, this must be within the range.
There must also be some leeway for the center point calibration.

It is getting a bit skinny now smiley

Only then do I
Code:
int speed = map(potValue, centre+deadBand, maxTravel, minSpeed, maxSpeed)
 for forward speed and Speed is within 0-255 for the PWM
3  Using Arduino / General Electronics / Re: Small potentiometer range to give full 0-5V? on: January 29, 2013, 02:19:12 am
Thanks guys for the replies sofar.

@Grumpy_Mike: Not sure what other vital information I'm with holding smiley I just don't have spare pins and want to stick to using the analog input. Another consideration is that encoders needs to be reset every time to find reference and the absolute one might be low cost, bust still expensive in time spend building and setting it up.

@silverxxx: You right about wanting to swing to close to the supply rails and use a low supply voltage. I remember something that the output becomes too erratic?

hmmm smiley I've been looking for  a solution for this for a while now. Looks like I then have to either get an actuator made for this, or go the mechanical way of increasing the travel of the pot.
Another idea I'm working on is using a slider pot, it has a shorter travel.
4  Using Arduino / General Electronics / Re: Small potentiometer range to give full 0-5V? on: January 28, 2013, 04:56:41 pm
Cost. Plus I would need 6 digital pins (3 per pedal for A,B and Z signals), which I don't have.
5  Using Arduino / General Electronics / Re: Small potentiometer range to give full 0-5V? on: January 28, 2013, 04:42:18 pm
Thought about that, but that would mean that I have to start from the one end of the pot which is near mechanical stop. I need to allow room for adjustment, electrically and mechanically.
But I won't rule this idea out completely.
6  Using Arduino / General Electronics / Small potentiometer range to give full 0-5V? on: January 28, 2013, 04:18:20 pm
Hi All
Here's the problem:
I want to control a potentiometer with a foot pedal. Pot is read by Uno analog input. If I connect the potentiometer direct to the foot pedal axis, I will get a a range of about 40 degrees movement on the pot. This is actually 20 degrees forward and 20 degrees backwards with center off (for forward and backward speed control).
I know there are commercial products out there such as actuators and foot pedals as well as means to extent the range of the pot mechanically, but this is a hobby project and I want to keep cost low and mechanically simple.

40 degrees on a standard 270 degree pot translates to a value of about 152 in the ADC register. This is too small for me, I would like to use as near to full range of the register as I need presision (well 70-80% will still be good).

My other idea is to electronically amplify this with opamps but I must have been sleeping when we studied opamps in class all those years ago. I can not come up with a circuit.

So, anybody got any ideas? With opamps, I want to input say 2.5V-3.5V and want to circuit to output about 0-5V which I then use as analog input. Upper and lower limit must be adjustable.
What would you call a opamp circuit like that (since just about all opamp circuits got names smiley )

Thanks
7  Development / Other Software Development / Re: PWM frequency library on: January 17, 2013, 04:13:36 am
Hi
I'm not quite clear as to these statements:
Quote
Has pin based (timer agnostic) functions
Has functions for getting and setting frequency at the timer level and pin level

I want to use your library to up the frequency of the PWM on my motor control project (motors are noisy) on a Uno. It is a twin motor control so I use pins 5, 6 for one and pins 9,10 for other.
Pins 5, 6 are timer0 and I don't want to mess with that timer.
So the next step would be to change it to pins 3, 11 to use the other timer. This would mean hacking my shield.
And that is why I don't understand the above. Does this mean I can map the PWM output to any pin?

I haven't used your library yet, just want to clear this first.

Thanks.
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