Hi Guys,
Thanks to your help my school buggy project is now complete. Well, the prototype is anyway - the kids have still got to finish theirs. It is set up like a car - a motor drives two wheels at the back and a servo steers two wheels at the front. It uses a 14M and HPWM to control the drive motor, the headlights switch on when the light level (LDR sensor) is low and an ultrasonic detector stops it bumping into things (most of the time). The 14M also talks to an 08M slave which controls the position of a servo and flashes the indicators. The kids are getting a lot out of the project and my learning has only been a couple of weeks ahead of theirs
Back at home I have just bought a 12V diesel transfer pump (complete with hoze and forecourt-like nozzle). This is to get biodiesel out of my storage tank and into the Land Rover and the wife's Volvo. At the moment I have to switch the pump on (one speed only) and then use the nozzle valve to control the flow. The valve seems to be full-on for about 90% of it's travel and when it gets close to the off position it is difficult to control and tends to "bounce" in your hand.
So as a benfit of the buggy project, I now know how to do PWM, so I thought I could use a PICaxe to control the motor speed based on the position of the nozzle lever. Even to the point where when the valve is fully closed the motor can be completely off. I was thinking I could attach a magnet to the moving valve lever and have a Hall Effect Sensor on the fixed part of the nozzle. I've never used a HES before but since the nozzle is all aluminium I think this would work. Questions:
1) HES - way to go or is there an easier way?
2) There will be 4m of wire from the nozzle following the hoze back to the pump so where should the elecronics be - pump end or nozzle end or (more likely I guess) split between the two ends. If split where in the electonics should the split be to avoid interference on the long leads?
3) Could I use some kind of cheap radio link between the two points to avoid cables altogether?
4) I think I should be able to do this with an 08M - PWMout on one pin and HES on another?
5) How do I work out how much current my pump is drawing? I have a DMM but it only goes upto 2A and I think the pump will be more. This is so I can decide what transistors to use.
6) I used Darlingtons on the buggy, I guess I should be looking at FETs for this beefier motor?
Hope you can help on this one - I've got to make the system easy to use for the wife
As an off-topic asside - does anyone know how the auto-cutoff device works on commercial forecourt pumps? I'm just intrigued...
Thanks to your help my school buggy project is now complete. Well, the prototype is anyway - the kids have still got to finish theirs. It is set up like a car - a motor drives two wheels at the back and a servo steers two wheels at the front. It uses a 14M and HPWM to control the drive motor, the headlights switch on when the light level (LDR sensor) is low and an ultrasonic detector stops it bumping into things (most of the time). The 14M also talks to an 08M slave which controls the position of a servo and flashes the indicators. The kids are getting a lot out of the project and my learning has only been a couple of weeks ahead of theirs
Back at home I have just bought a 12V diesel transfer pump (complete with hoze and forecourt-like nozzle). This is to get biodiesel out of my storage tank and into the Land Rover and the wife's Volvo. At the moment I have to switch the pump on (one speed only) and then use the nozzle valve to control the flow. The valve seems to be full-on for about 90% of it's travel and when it gets close to the off position it is difficult to control and tends to "bounce" in your hand.
So as a benfit of the buggy project, I now know how to do PWM, so I thought I could use a PICaxe to control the motor speed based on the position of the nozzle lever. Even to the point where when the valve is fully closed the motor can be completely off. I was thinking I could attach a magnet to the moving valve lever and have a Hall Effect Sensor on the fixed part of the nozzle. I've never used a HES before but since the nozzle is all aluminium I think this would work. Questions:
1) HES - way to go or is there an easier way?
2) There will be 4m of wire from the nozzle following the hoze back to the pump so where should the elecronics be - pump end or nozzle end or (more likely I guess) split between the two ends. If split where in the electonics should the split be to avoid interference on the long leads?
3) Could I use some kind of cheap radio link between the two points to avoid cables altogether?
4) I think I should be able to do this with an 08M - PWMout on one pin and HES on another?
5) How do I work out how much current my pump is drawing? I have a DMM but it only goes upto 2A and I think the pump will be more. This is so I can decide what transistors to use.
6) I used Darlingtons on the buggy, I guess I should be looking at FETs for this beefier motor?
Hope you can help on this one - I've got to make the system easy to use for the wife
As an off-topic asside - does anyone know how the auto-cutoff device works on commercial forecourt pumps? I'm just intrigued...