19 replies to this topic

[Ethel]

How about using a 2nd pot as a position sensor? I know it negates much the reason for using a stepper.

 

There must be a sketch already written to find somewhere. You can't be the first to want to control  stepper position with a pot. Youtube can be a good place to look.

[Icey]

I've seen these projects float around forums for years and it's sad to say, nearly all of them fail.

 

The challenge with any small automotive electronics project is noise. Cars are very harsh environments electrically (especially classics). You may be able to buy a solution off the shelf these days but previously most of the development effort went into the power supply, not the code.

 

In parallel to this, you have physical environmental challenges to contend with. Are the components you're using rated for the extremes a car will see - freezing/boiling temperatures, high levels of dirt/dust, water.

When these are considered alongside the alternative (a longer, relocated cable) it never stacks up, and if you do get it going the first time you want to use your car and it doesn't work because one of your new components has failed you just kick yourself harder.

 

This all sounds very negative (and I guess it is) - but just go into this informed, what you're doing isn't easy expect to fail many times but at the same time learn quite a bit about electronics. I did the same!

 

Edit:

And just to throw in something which might be counted as a contribution - why use rotary action? Why not retain the cable to bring the components into the cabin and use a linear actuator to push/pull.

 

 

Edited by Icey, 13 February 2018 - 11:07 AM.

[paulrockliffe]

Thanks, I've no idea how it'll work, not under any illusions it'll be easy and work perfectly. I'm leaving the cable attached, so if it fails it'll just need the outer sleeve clipping back in. Absolute worse case you have to jam the choke on with something and wait while the engine warms up. The point of the project is really to learn something new.

You make a good point about a linear actuator, I'll look at that as it'll be easier to keep the existing arrangement rather than make up a bracket for the stepper.

I've got the basic code working now, turn the rotary encoder and the motor follows. Press the button to reset the motor to the starting position. Going to add an LED display next so I can see how much choke is on next.

[Spider]

A different approach to the Stepper Motor to possibly consider as an alternative, not that I'd for one moment suggest the stepper is no good though, but as Icey mentioned, noise maybe a problem.

 

I've done Heater Controls (both for the Water and the Flap) using Servos as used in RC Models. I found a very simple Driver Circuit for them that worked from a Pot. I felt it quite simple and worked very reliably. There s a huge range of these Servos available.

[Icey]

I've done Heater Controls (both for the Water and the Flap) using Servos as used in RC Models. I found a very simple Driver Circuit for them that worked from a Pot. I felt it quite simple and worked very reliably. There s a huge range of these Servos available.

 

You can get some monsters these days with full metal gears and potentiometer feedback. You'd likely be able to build a very noise tolerant driver circuit with a 555 chip.

 

Key is building a 5v supply that can take out the bulk of the noise, a quick google suggests that there may be buck converters now available specifically for automotive applications - I'd be interested to know if anyone has used them and what they are like.