openinverter forum

So I've ordered an Audi vacuum pump https://www.ebay.co.uk/itm/123919350659
I plan to use the Freelander Vacuum chamber but need a sensor so while searching for the pump came across and ordered this. https://www.ebay.co.uk/itm/201317171485
TBH I'm not certain it will work as I need it to but it's only 20 quid so worth a punt. Anyone else know if this is a suitable sensor for an EV conversion?

Alibro wrote: ↑Tue Nov 17, 2020 7:37 pm So I've ordered an Audi vacuum pump https://www.ebay.co.uk/itm/123919350659
I plan to use the Freelander Vacuum chamber but need a sensor so while searching for the pump came across and ordered this. https://www.ebay.co.uk/itm/201317171485
TBH I'm not certain it will work as I need it to but it's only 20 quid so worth a punt. Anyone else know if this is a suitable sensor for an EV conversion?

Yes the sensor outputs a voltage proportional to pressure/vacuum (viewtopic.php?f=9&t=335&start=50#p9183). I use it in both my conversions and use a simple hysteresis controller that turns on the pump at about 1.6V from the sensor and turns it off at 1.4V. I also have a hardware version of that controller. Let me know if you're interested.

johu wrote: ↑Thu Nov 19, 2020 12:15 pm

Alibro wrote: ↑Tue Nov 17, 2020 7:37 pm So I've ordered an Audi vacuum pump https://www.ebay.co.uk/itm/123919350659
I plan to use the Freelander Vacuum chamber but need a sensor so while searching for the pump came across and ordered this. https://www.ebay.co.uk/itm/201317171485
TBH I'm not certain it will work as I need it to but it's only 20 quid so worth a punt. Anyone else know if this is a suitable sensor for an EV conversion?

Yes the sensor outputs a voltage proportional to pressure/vacuum (viewtopic.php?f=9&t=335&start=50#p9183). I use it in both my conversions and use a simple hysteresis controller that turns on the pump at about 1.6V from the sensor and turns it off at 1.4V. I also have a hardware version of that controller. Let me know if you're interested.

I was thinking of using an Arduino to control the vacuum pump but hadn't figured out how to do it yet so if you have something ready to go then I'm interested.

Basically this. The MOSFET is strong enough to run the pump directly.

If there is more demand for this I can put it on the shop. Maybe even including the vacuum sensor. Anyone?

I could be, if the price is right

Could be like 20€ for just the populated PCB or 90€ for PCB+sensor+wire harness.

Sounds reasonable, but I've just noticed you've implemented it in stm32-car that I'm ripping off so might not need one after all.

johu wrote: ↑Thu Nov 19, 2020 8:15 pm Basically this. The MOSFET is strong enough to run the pump directly.

So how do we program the hysteresis or is it set and forget?
I only ask for others here as I will find out when it arrives.

It's hard coded The RC filter (R2/C1+C2) is responsible

johu wrote: ↑Fri Nov 20, 2020 8:10 am If there is more demand for this I can put it on the shop. Maybe even including the vacuum sensor. Anyone?

I'd be up for one of these. Keeps things nice and simple and I have the sensor.

johu wrote: ↑Fri Nov 20, 2020 7:51 pm It's hard coded The RC filter (R2/C1+C2) is responsible

I could use one of these too. Just bench tested the Bosch 0265 005 321 Vacuum Brake Servo Sensor from the Zafira C. It works off 5v. At no vac pressure, it sites at 0.7v and when you get to max vac, it hits just over 4v. Reckon the populated PCB could handle this Johannes?

I think with the inversion stage skipped it should do. Gotta ltspice that.
Basically T2 and R4 removed and collector of T1 bridged over to R5. And voltage divider R1/R2 adjusted so T1 activates at 4V or 3V, whichever is appropriate.

If there's any extra work involved johannes for the bosch sensor, I'll gladly fork out for a working unit

johu wrote: ↑Sun Nov 22, 2020 9:58 pm I think with the inversion stage skipped it should do. Gotta ltspice that.
Basically T2 and R4 removed and collector of T1 bridged over to R5. And voltage divider R1/R2 adjusted so T1 activates at 4V or 3V, whichever is appropriate.

Thanks again Johannes for sending the unit on. So, as outlined, remove T2 and R4 and bridge the T1 collector over to R5. Do both R1 and R2 need to be swapped to achieve the trigger points? Any pointers for someone who is rusty on his electronics? I would have it activating when it drops below 3V.

Yes, like drawn
You could replace R2 with 15k or R1 with 3k3

Brill. Thanks. I'll have a play around

So, all components removed and tracks jumpered up. Swapped R2 out for a 22k for now as it's all i had lying about.
Am I right with the wiring here on each of the connectors?

Yes looks correct, except input GND is on yellow, not orange.
For startup testing, I'd expect the pump to be ON as long as no sensor is connected. Then as "5V op" approaches 3V the pump should turn off. Also check "5V ip" for correct value before connecting the sensor.

Cool
OK, i'm on the right track. I rigged it all up as you described, changing the ground, stepped through the test before I connected up the sensor and after and here's how I got on. No activity from the pump at all. Powered pump itself outside the circuit, all good. Wired up, no go. We do however have our 5v out the other side for the sensor and a 0.4v ref voltage fed back with no vacuum. Here are a few test measurements I made WITH the sensor connected. Anything obvious? I do have the 12v ip/op connected the right way, yes?

Ah, the pump output (red) is switched GND

Excellent
Thanks for clarifying that. Think I'm almost there.
Switched ground Red to ground of pump. Brown to 12v+ on battery. Yellow to 12v- of battery.
Sensor voltage now 0.9v after vacuum purge.

Connect 12v+ to the battery, away she goes. Ref voltage climbs, gets to 4.3v and no further, motor keep running. I am guessing I am at the point now I need to change either R1 (currently 4k7) or R2 (currently 22k) to get the trigger point to about 3v, no?

Cookie6000 wrote: ↑Sat Dec 19, 2020 3:54 pm Excellent
Thanks for clarifying that. Think I'm almost there.
Switched ground Red to ground of pump. Brown to 12v+ on battery. Yellow to 12v- of battery.
Sensor voltage now 0.9v after vacuum purge.

Connect 12v+ to the battery, away she goes. Ref voltage climbs, gets to 4.3v and no further, motor keep running. I am guessing I am at the point now I need to change either R1 (currently 4k7) or R2 (currently 22k) to get the trigger point to about 3v, no?
20201219_153813.jpg

I actually remember i saw similar circuit on Opel Astra or Vectra. No analog sensing though, only MOSFET triggered by underpressure switch.

Alibro wrote: ↑Tue Nov 17, 2020 7:37 pm Anyone else know if this is a suitable sensor for an EV conversion?

You could also consider using an adjustable switch
https://www.evcreate.nl/shop/brakes-whe ... um-switch/

Anyone got any info on the vacuum sensor from a Corsa E?
Been looking for wiring diagrams for a few hours but not come up with anything. 3 pins