I am installing an aftermarket air conditioning unit in a '59 Edsel.
Since playing with the arduino I recognize this system as a
micro controller that takes a 5 pos. Switch and 2 10k slide pots for input
And outputs to 3 servos and 2 relays.
The 2 10k pots are set up to connect to the slide levers that operated the original
Cable controls. Then a calibration procedure maps the installed range of the pots.
The problem is that one of the levers on this particular car originally controlled
2 cables one for the first half of the travel and a second for the last half.
I could connect to just one of those and that is what the manufacturer suggests, but I worry that the short travel of both the lever and the pot would be too sensitive for the 11 position range.
1 Is it possible to substitute 2 5k pots in series for the 10k ?
There are 3 wires from the controller I assume these are power,ground and the wiper.
2 How should it be wired?
I am assuming that the calibration procedure should work as long as I present it with a resistance within a 0-10k range.
The basic Arduino can measure 1024 steps over the full travel of a pot. There's noise and other factors so the usable resolution can be much lower than this. Even if there's only 64 readable steps over full travel and your actual hardware only moves 1/6th of this then there's enough resolution do do what you want to do.
The problem is that one of the levers on this particular car originally controlled
2 cables one for the first half of the travel and a second for the last half.
That really doesn't make sense to me. Does that mean that the 2nd control doesn't do anything until the 1st control is at maximum?
1 Is it possible to substitute 2 5k pots in series for the 10k ?
There are 3 wires from the controller I assume these are power,ground and the wiper.
No. The two controls may "conflict" with each other.
I can't imagine having two volume controls on a stereo system or two temperature controls on a heater...
The only way I know of to use 2 pots to control one thing is to make a course control and a fine control. In that case, the output (wiper) of the 1st pot goes to the top of the 2nd pot. I've seen that done, but it's tricky because you have to reset the fine control to the center before adjusting/re-adjusting the course control (or the fine-control might be too near it's limit to be effective).
That's really not done too much anymore because with digital electronics you can use a rotary encoder and there are much better "tricks" for course & fine adjustment.
Yes the lever is a mechanical set up that pulls the first control to max during
the first half of it's travel then engages the second control and moves it to
max during the second half of it's travel.
And yes the manufacturer has said that it will function correctly using The one control
And only half the lever travel. But that is a hack solution that crowds all my functions to one side . I would like to correct that situation.
If you can get the physical job done to control a potentiometer with a lever, the rest will be easy.
The software can split up the input in two ranges. Your potentiometer does not have to go all the way. The analog input can give you 1024 values, more than you need for temparature control.
so mechanically the potentiometer does not require a 270 degree turn - if you can only a 45 degree turn it will also be ok. this will give you more than 100 values, more than enough for temperature control.
Just take the maximum value you will get an split it in two. The lower range will control one motor/stepper/whatever, the upper range the other one.
so the software is not the problem.
just tell us what the maximum value you will see and you will get lots of help for designing your code.
You can do the mechanical part whatever way you want. Whatever is easiest.
One pot for the main lever. Two pots, one for each cable lever. 2x 10k, 2x 5k, whatever.
Everything can be controlled in software.
e.g don't use the value of the second pot if the first one hasn't reached it's maximum value yet.
It might be easiest, software wise, to connect each pot to it's own analogue input.
Leo..
What you have not explained is what potentiometers and an Arduino have to do with this in the first place.
I note you have been looking at other aspects of "computerising" this refit - gauges and remote locking. There might be certain jobs for which a MCU is useful, but it does not always follow by any means.
it is quite usual for a control lever on the heater controls to actuate two (possibly more) functions, notably the coolant valve and the air conditioning control or the various flaps which direct the air, so no surprise there.
As always though, a precise description of what the original lever actually did and what interface is required to the air conditioning unit, would be much more productive.
Please tell us what your specific microprocessor is expecting to see - and some persons like me will try to find out how to get the right input for your system
You can reprogram your device (microprocessor) to do what you want it to do
I am just afraid that Arduino people cannot help you with an unknown/unnamed device or microprocessor.
Reprogramming this Is not possible for me.
I have now gotten it hooked and have done some testing.
The pot is set up as a voltage divider with 5v on one end ground on the other
So the wiper outputs 0-5v
this is mapped with a calibration procedure to control 3 servos in 11 positions
The first position has floor vent door open and the other 2 closed .
The second position closes the floor vent 20% and opens the defrost vent 20%
This continues to the center position where the defrost vent is fully open and the other 2 are closed. It then continues to blend from the defrost vent to the dash vents. Where the dash vent is the only one open in the last position. There are detents in the first,center and last positions.
Paul_B's microswitch idea will work if I can find a way to mount one.
I will likely try this unless I can find another simple circuit that would work.
