woodsy144
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| posted on 15/7/24 at 11:51 PM |
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Polo / VW Group Electric Rear Calipers - retrofitted???
Hello,
Been doing some research and fumbling around, and came across the electric park brake caliper for the polo.
the interesting thing, is the motor for the EPS is only 2 pin.
https://www.trwaftermarket.com/en/news/electric-parking-brake/?VehicleType=News
Now, i would make the super high level inference that the motor is a 'dumb' setup, with only power and group.
Which would lean me to think that this maybe a good candidate for kit vehicles.
Question - has anyone played around with such calipers??? Anyone have any experience with them?
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car man
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| posted on 16/7/24 at 08:52 AM |
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I have the vw passat ones on my car with a small microcontroller and two buttons. It passed the IVA no problem still working.
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gremlin1234
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| posted on 16/7/24 at 09:49 AM |
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I have not played with them myself,
but the wiring would be fairy simple, you just power it until the motor stalls, (detected by the current drawn)
I did see some of the most advanced systems actually check the temperature of the disk, and compensate as the disk cools down, (ie reapply the force
after a few minutes)
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gremlin1234
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| posted on 16/7/24 at 09:50 AM |
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quote:
Originally posted by car man
I have the vw passat ones on my car with a small microcontroller and two buttons. It passed the IVA no problem still working.
that's interesting, do you please have a link for the microcontroller
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car man
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| posted on 16/7/24 at 10:28 AM |
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The microcontroller was a pic16f886.
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JAG
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| posted on 16/7/24 at 11:29 AM |
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You're correct about the motor on the EPB calipers - it is a dumb motor with a gearbox.
12v polarity is switched around to apply & release. It uses a current cut off device to reach the desired clamp force.
On a production car it can perform "drive-away-release" "hot-disc-reclamp" "service-brake-support" plus a bunch of other
clever stuff. However you'd need a whole host of other 'stuff' to achieve that and it's not really practical or necessary on a kit
car.
For our cars you just need an on/off switch and a controller that can sense and cut-off when a current is reached. It would be useful to be able to
adjust the cut-off value.
On a large saloon or SUV the cut-off is approx' 15 amps to achieve 20-25 kN clamp load.
You wouldn't need anything like that for a Se7en-esque kit car.
Has anyone designed a suitable controller?
Could you share the details?
[Edited on 16/7/24 by JAG]
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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coyoteboy
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| posted on 16/7/24 at 11:59 AM |
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Super cheap and simple, I considered it for a while but I was under the impression the IVA required mechanical latching - I know the worm drives are
anti-backdrive but they're not normally that pragmatic  If it were a thing people wanted, I could fairly quickly lob a cheap kit or product
together for funsees.
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woodsy144
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| posted on 16/7/24 at 12:31 PM |
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quote:
Originally posted by coyoteboy
Super cheap and simple, I considered it for a while but I was under the impression the IVA required mechanical latching - I know the worm drives are
anti-backdrive but they're not normally that pragmatic If it were a thing people wanted, I could fairly quickly lob a cheap kit or product
together for funsees.
Definitely keen to know more.
A bit of a brain dump, but would like an over ride on and off and an current adjuster.
Anything else??
Secondly, I am assuming that when battery power is off, is it locked on??
[Edited on 16/7/24 by woodsy144]
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JAG
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| posted on 16/7/24 at 12:43 PM |
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quote:
I considered it for a while but I was under the impression the IVA required mechanical latching
quote:
when battery power is off, is it locked on??
The mechanical latching is the same for production cars and they're OK with the EPB calipers. Basically the gearbox prevents the parkbrake from
releasing once it's been applied, even without the 12v power. It works for production type approval so it works for IVA.
There are two basic types. The worm & wheel gearbox (from Continental and a few others) and the beltdrive with an epicyclic gearbox (from
TRW/ZF).
[Edited on 16/7/24 by JAG]
[Edited on 16/7/24 by JAG]
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Half Finished
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| posted on 16/7/24 at 01:07 PM |
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For a controller, this would work well out of the box. I've used one before in a similar application. The current and speed can be set with a
potentiometer and the motor direction is then set by two buttons. There is also a 50amp version and an external programmer available.
https://uk.rs-online.com/web/p/motor-controllers/7736841?gb=s
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gremlin1234
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| posted on 16/7/24 at 01:16 PM |
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quote:
Originally posted by Half Finished
For a controller, this would work well out of the box. I've used one before in a similar application. The current and speed can be set with a
potentiometer and the motor direction is then set by two buttons. There is also a 50amp version and an external programmer available.
https://uk.rs-online.com/web/p/motor-controllers/7736841?gb=s
I guess you would require a controller like this, for each caliper
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gremlin1234
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| posted on 16/7/24 at 01:19 PM |
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quote:
Originally posted by car man
The microcontroller was a pic16f886.
Thank You
could you also please share the circuit used, and the programming? or where to get a unit commercially
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Half Finished
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| posted on 16/7/24 at 01:30 PM |
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quote:
Originally posted by gremlin1234
quote:
Originally posted by Half Finished
For a controller, this would work well out of the box. I've used one before in a similar application. The current and speed can be set with a
potentiometer and the motor direction is then set by two buttons. There is also a 50amp version and an external programmer available.
https://uk.rs-online.com/web/p/motor-controllers/7736841?gb=s
I guess you would require a controller like this, for each caliper
Im not sure if they would get out of phase if you drive them in parallel? They are hitting end stops each cycle. As long as the wire lengths are
identical.
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JAG
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| posted on 16/7/24 at 01:45 PM |
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quote:
For a controller, this would work well out of the box
That looks like it would work. It's 15 amps per caliper on a large saloon or SUV that weighs over 1.5 tons.
I suspect our cars would be very capable at 5-8 amps per caliper. So I think one of these units, connected to both calipers, would be sufficient.
Can someone show me how the switch and calipers would be connected?
Draw a diagram perhaps?
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Mr Whippy
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| posted on 16/7/24 at 02:50 PM |
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I have this on the golf, as the car has hill hold it's fine but without that I can imagine it would be crap as there's zero 'feel"
when it's about to let go. It's really all or nothing as far as braking is concerned.
Try it in your tin top, ram on the handbrake fully on in your car next time your on a hill and then let it go all at once, see how you get on with
hill starts  
Fame is when your old car is plastered all over the internet
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Half Finished
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| posted on 16/7/24 at 04:44 PM |
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I linked to the older version before, there is a newer version with some additional features. They also support up to 30A for 5 seconds so should
cover 2 calipers. I'm not affiliated with them, I just used one in a university project.
I think it would be pragmatic to implement some kind of technical interlock so it's not easy to accidentally trigger the handbrake whilst
moving. Normally you would need to press and hold the EPB button for activation whilst moving.
What hubs would the polo calipers fit too? I'm tempted to go this route myself with mx5 hubs.
https://uk.rs-online.com/web/p/motor-controllers/1837330
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adithorp
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| posted on 16/7/24 at 09:53 PM |
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Controlling when the motor stops when applying is one thing but how fo you control how far it goes when disengaging and adjusts that for wear?
If it goes fully back it'll take several seconds to reapply. A timer circuit maybe but it'd have to have a lockout to stop it
releasing/backing off unless the brake was applied.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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coyoteboy
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| posted on 16/7/24 at 10:26 PM |
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quote:
Originally posted by Mr Whippy
I have this on the golf, as the car has hill hold it's fine but without that I can imagine it would be crap as there's zero 'feel"
when it's about to let go. It's really all or nothing as far as braking is concerned.
Try it in your tin top, ram on the handbrake fully on in your car next time your on a hill and then let it go all at once, see how you get on with
hill starts
Does anyone use the handbrake for hill stats after their driving test? Don't think i have in 25 years of driving up hill and down dale, i can
balance the footbrake and clutch bite just fine
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coyoteboy
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| posted on 16/7/24 at 10:27 PM |
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quote:
Originally posted by adithorp
Controlling when the motor stops when applying is one thing but how fo you control how far it goes when disengaging and adjusts that for wear?
If it goes fully back it'll take several seconds to reapply. A timer circuit maybe but it'd have to have a lockout to stop it
releasing/backing off unless the brake was applied.
I think by default they go all the way back, whenever i hear them in the car park thru go a good second or so, and thats a fair old travel. The
piston usually do the auto adjustment and the motor takes up the last slack
[Edited on 16/7/2024 by coyoteboy]
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adithorp
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| posted on 16/7/24 at 11:04 PM |
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There's a big difference between how long the take to disengage and how long it takes to do a full wind back in service mode when changing pads
and again switching out of service setting (done 2 today).
Keep holding on the clutch though; keeps garages in work replacing them.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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car man
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| posted on 17/7/24 at 08:59 AM |
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This is a good motor control unit
https://thepihut.com/products/15a-single-dc-motor-driver?variant=27740754833¤cy=GBP&utm_medium=product_sync&utm_source=google&ut
m_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gclid=CjwKCAjw1920BhA3EiwAJT3lSdvk5lviku0UTqq_QnGjZbcF4UWLOLh9HYQe0n-vH1Y1movV
4Tj61xoCTZAQAvD_BwE
I back my motor off for just 1 second.
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JAG
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| posted on 17/7/24 at 11:56 AM |
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Thinking more...
Adjustment for pad wear is automatic and built into the mechanism behind the caliper piston. Apply/release times are not affected by pad wear.
The motor controller is a great start BUT we also need something with software (that we can program/modify) to sit between the EPB Switch (in the
cockpit) and the Motor Controller. Could we use a Raspberry Pi or Arduino device?
This would control the apply/release current and timing.
Plus a suitable EPB switch - it should have an ON/OFF/ON configuration to enable apply and release.
I think the final system would look like this;
[EPB Switch] - [Raspberry Pi or Arduino] - [Motor Controller] - [2 x EPB Calipers]
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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coyoteboy
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| posted on 17/7/24 at 01:35 PM |
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quote:
Originally posted by adithorp
Keep holding on the clutch though; keeps garages in work replacing them.
Owned 4 manual cars since 1998, I still own 3 of them. I've replaced 1 clutch in 300K miles.
A Peugeot 205 that managed 85K to 145K miles in my name, still on original clutch when written off.
A Celica GT4 which managed 84K to 115K miles, clutch gone at 110K miles due to a 4WD launch that shattered the friction plate - plenty of meat left on
both the plate and the fly.
A Peugeot 306 HDI which I had from 75K miles to 250K miles and just started to slip at 250K (just had new clutch but sits unused).
A 370Z which I've taken from 86K miles to 125K miles still on stock clutch (but this has hill-hold that works above about a 10 degree slope to be
fair).
Can't be that worrying eh
Not like you hold it on the clutch the whole time eh, you hold it on the foot brake and then at the last second drop to bite and move off, if you
can't do that without rolling less than an inch you shouldn't be driving.
[Edited on 17/7/2024 by coyoteboy]
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coyoteboy
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| posted on 17/7/24 at 03:06 PM |
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quote:
Originally posted by JAG
Thinking more...
Adjustment for pad wear is automatic and built into the mechanism behind the caliper piston. Apply/release times are not affected by pad wear.
The motor controller is a great start BUT we also need something with software (that we can program/modify) to sit between the EPB Switch (in the
cockpit) and the Motor Controller. Could we use a Raspberry Pi or Arduino device?
This would control the apply/release current and timing.
Plus a suitable EPB switch - it should have an ON/OFF/ON configuration to enable apply and release.
I think the final system would look like this;
[EPB Switch] - [Raspberry Pi or Arduino] - [Motor Controller] - [2 x EPB Calipers]
Arduino is more than enough to do this, a pi would be a mistake. Your biggest issue is how long to back-drive to release, nothing 5 mins of testing
won't solve.
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scudderfish
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| posted on 17/7/24 at 04:15 PM |
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quote:
Originally posted by coyoteboy
I think the final system would look like this;
[EPB Switch] - [Raspberry Pi or Arduino] - [Motor Controller] - [2 x EPB Calipers]
Arduino is more than enough to do this, a pi would be a mistake. Your biggest issue is how long to back-drive to release, nothing 5 mins of testing
won't solve.
ESP32 and Wifi enable your handbrake!
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