Saturday, March 21, 2015

Electrical Planning

I set up the controller on the work bench today.

I am trying to set up a good range on the onboard control.  The 5k pot the machine had would go from 0 to 12 MPH in in a 1/3rd of a turn.  Much too fast for that form of control.

Here is some data I gathered from trials...
Start angle, Max speed, Resistor, Pot, Thought
120, 11.8, 0, 5k,  way too fast & narrow range
0, 9.8, 0, 0, what happens with nothing is connected
90, 2, 3.3K, 1K, max speed is too slow, good range
0, 6.2, 2.2K, 1K, good max speed but slow speed is 2.4 mph if start angle was 10 degrees this would be perfect
90, 6, 2.2K 2.5K, this is good, slow end starts late, not sure how to manage.
10, 3, 3K, 1K,  good but slow
110, 4, 2.68, 2.5K  spot on with huge low end deadband

OK I am doing this the silly way.  I have a meter... I should measure across PH and PW and get a table of speeds for each resistance.  With the 5k pot.  My electrical minded brother said I did it wrong. I kept the pot hooked up to the source when I measured, which skewed my readings.  I threw out the suspect data, and after talking with him and realizing that I had similar results as him we did have similar results: 1k deadband at bottom 3k of range and 1k of deadband at top.  Look at the poly lines not the linear ones.  The chart is messy because the experiment was poor.

Note that the controller works backwards, more resistance is full go, no resistances is stop.  Not safe in our mind since we have a tether that can separate (infinite resistance = fasted speed and no way to stop.)

So for on-board control I want a max speed of 4mph, that is 2K Then I need to make up the rest with 3K of fixed resistors. At least that is the theory. I am going to try 3k fixed with 1k pot & 2.5k pot to see which I like better.  I will also try 2.5k fixed with both.  But first dinner....

OK I am back... Added some new values to the table above in Blue
2.68k fixed with a 2.5k pot has a max speed of 4 and 110 degrees of dead band at the zero end.
3k fixed with a 1k pot has a max speed of 3 and about 10 degrees of dead band at zero.
I need to order a pot that will fit in the machine online anyway, I am thinking of getting one each of 1K, 1.5K, 2K, and 2.5K  Then I can play around a bit more to dial in what I want.  I am leaning towards the 3K 1K setup with 3mph max as a good option.  Note that 2.68K & 1K did not stop at the low end, a 2.68 and 1.5 might.

Note:  the pacesetter is really supposed to be center off.  I found out after wiring up the whole machines that I should have worked with both directions when setting the resistor and pot.  I was able to get it to work with what I got but top speed in forward is 4mph and 2 in reverse.  Forward has no deadband, reverse has about 30 degrees.

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