Hardware threshold switch for brake vacuum pump

[nkiernan]

Thanks Johu,
I'll try source the components myself to and swap them out.

[nkiernan]

Hi Johu,
Quick query on repairing these boards, is it all four caps that need to be replaced or just one of the four?

[johu]

The one closest to the 5V regulator

[nkiernan]

The one closest to the 5V regulator

Thanks Johu

[et0]

One thought on the electronic pump switch: what about a PCB mounted pressure sensor - these are low cost and could make for a neat solution - no need to find a specific automotive sensor and connector etc.

The Megasquirt ECU uses that approach for manifold vacuum sensing, you just plug a small hose into its enclosure, job done.

[johu]

Sounds like a neat option. Probably JLCPCB don't stock one but it could just be retrofitted if needed. Would still keep the external one as an option (in my car it was already fitted)

[ErikvHilten]

Hi Johu,
Ordered the electronic brake pressure switch and received it yesterday. I hooked it up to 12V car battery and a standard UP28 vacuum pump and vacuum sensor. Worked directly, and got -0.46 bar vacuum. Hysteresis I found is not so much, maybe 0.05 bar in my case.

Unfortunately when I wanted to show the succes to my wife the pump kept on running. I now measure 12V on the 5V output. On the 5V regulator it says 1117 // 50 2045. @Johu, can you help out? Is the regulator or a capacitor broken?

[johu]

Argh, that sucks. It is already the newer regulator that can take up to 20V supposedly - maybe they don't all work up to spec. I think I need to revise the design and put a resistor and TVR diode before the regulator.
Can you order a new regulator and I refund you parts of the price? Let me know the order number

[ErikvHilten]

Hi Johu, I prefer if you can send me a replacement regulator then I'll try to solder it on. This would save high shipping costs and minimum order qty many part suppliers use. My order ID number: 709. How would you suggest to connect the resistor and TVR diode? Do you think it is possible to adapt the board and solder it on? Thanks.

[johu]

Ok, I will send you a board with a regulator I sourced locally (no more regulators left). For starters a TVS diode across the reg input would already help.
So for anyone who haven't tested their board yet: solder a roughly 15V TVS diode across the outer regulator pins.

So all modules I send out now will have this fitted.

[ErikvHilten]

Hi Johu, Received the board with diode and tested it. Thank you, it now works well. I've sent you back the original board.

[nkiernan]

So for anyone who haven't tested their board yet: solder a roughly 15V TVS diode across the outer regulator pins.

So all modules I send out now will have this fitted.

Hi Johu,
So sounds like I should also fit the TVS diode. Not sure what exact specs are needed so wanted to check if something like this would work?

https://www.ebay.co.uk/itm/254490641826 ... SwLABeKcYW

[johu]

Yes that should do. I found a 15V TVS only starts conducting at about 18V so maybe even go for around 13V or whatever comes close

[nkiernan]

Thanks Johu

[johu]

I just ordered a new batch and that will have the TVS and an additional resistor fitted. In case of an over voltage (say, above 16V) that resistor might burn out and needs replacing but the voltage regulator will be safe.

[RetroZero]

Can't wait for them to be back on the shop list. Ordered vacuum pump and pressure sensor in the meantime

[RetroZero]

Hi Johannes, any idea on delay for your next order?

[johu]

oh, seems I never updated stock. It's available.

[RetroZero]

Got my setup running. Is anyone using an additional reservoir for vacuum? Mine switches on and off a few times when it gets to cut off value.

[eee291]

My vacuum switch died. I hooked up everything on the Bench and it was working fine.
I disconnected 12V from the board while the pump was cycling and I saw a small spark on that 1117 component.
Now the 5V terminal is outputting only 1V.

[johu]

Oh, then the turnoff spike had nowhere to go. Is the version with TVS diode protecting the 1117? If in doubt post a pic

[eee291]

I bought it like a month ago. I'm pretty sure it has the diode in there.
If I try this again I should switch power from the pump directly, right?

[johu]

ok, that one should survive most mistreatment. Can you check R6? Should be 10 Ohm

[eee291]

I think R6 is dead, the resistance started at 6Mohm and it just keeps climbing up to 11Mohm and beyond the longer I measure it.
I'll try with a through hole resistor that I have and report back.

[johu]

ok, just replace it. Acted as a fuse so to speak