# [EVDL] Brake Vacuum Pump Relay cycling - need delay timer?



## EVDL List (Jul 27, 2007)

Hi gang!

Does anyone know where I could find a 12 delay relay? And is anyone
else having this problem? Here's what I'd like to do:

When the brake vacuum pump draws down the pressure in my little tank,
I'd like it to run an extra 5 seconds maybe - drawing the pressure far
enough below the switchpoint that the switch won't click on and off
repeatedly when I hit bumps, etc. It currently with on-off-cycle a few
times within a second when driving - I assume it is a sensitivity issue
in the switch. If I manually override the switch, and let the pump run
for an extra few seconds, it never cycles again until I hit the brakes. 
I'm pretty sure this cycling is rough on the pump as well as the relay
- It toasted a relay with the rapid switching - failed in the on
position.

Specs: 
Hobbs Switch 17" (I think)
Thompson-Gardener pump 
These came with my ElectroAuto kit.

Here's what I've found is my searching, but I don't think 12 volts will
drive this thing. Also, is "Delay on Break" what I should be looking
for?

http://www.grainger.com/Grainger/items/4E234


Thanks all - I've enjoyed ~300 gas free miles. And when a relay
arrives, I'll actually have HEAT! It's a high of 1 degree today in
Iowa AAH!!

Andy

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## EVDL List (Jul 27, 2007)

Usually, people use a vacuum switch that has "hysteresis" built in -
it turns on when the vacuum falls to 18 inHg, and doesn't turn back
off until it rises to 22 inHg.

However, a time delay relay will work, too. Yes, Delay on Break is
what you want - that means it will run for a little while longer
before turning off.

I think we have some time delay relays in a lab at work that are
adjustable enough to work for you and has 12VDC coils. Unless you find
something good sooner, I'll check the maker/model number on Monday.

Even though 1.5A isn't enough to control the vacuum pump, that's OK:
you could just use the output of the time delay relay to control the
coil of a regular relay. It adds a bit of wiring complexity and an
extra part, but if it gets your goal, that's OK.

-Morgan LaMoore



> <[email protected]> wrote:
> >
> > Hi gang!
> >
> ...


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## EVDL List (Jul 27, 2007)

Hello Andy,

Just go to your local parts store and pick up a Bosch 12 volt 75 amp rated 
relay. I use them to operated my electric power steering, pumps and fans. 
While you are there, have them look up Bosch vacuum switches for you.

The Bosch relays come with a enclosure, chassis mounting and set screw box 
lugs wire attachments.

It is best to use a vacuum switch that has a differential you can adjust 
like on at 15 in.hg and off at 20 to 22 in.hg.

The vacuum switch contacts are not design to run power circuits, only 
control circuits. Have the vacuum switch operated the above type relay 
(actual technically call a contactor which switches power circuits.)

You can also get relays, contactors and time delay relay at:

www.surplusales.com

www.allelectrolnics.com

Roland




----- Original Message ----- 
From: <[email protected]>
To: <[email protected]>
Sent: Saturday, January 19, 2008 2:43 PM
Subject: [EVDL] Brake Vacuum Pump Relay cycling - need delay timer?


>
> Hi gang!
>
> Does anyone know where I could find a 12 delay relay? And is anyone
> else having this problem? Here's what I'd like to do:
>
> When the brake vacuum pump draws down the pressure in my little tank,
> I'd like it to run an extra 5 seconds maybe - drawing the pressure far
> enough below the switchpoint that the switch won't click on and off
> repeatedly when I hit bumps, etc. It currently with on-off-cycle a few
> times within a second when driving - I assume it is a sensitivity issue
> in the switch. If I manually override the switch, and let the pump run
> for an extra few seconds, it never cycles again until I hit the brakes.
> I'm pretty sure this cycling is rough on the pump as well as the relay
> - It toasted a relay with the rapid switching - failed in the on
> position.
>
> Specs:
> Hobbs Switch 17" (I think)
> Thompson-Gardener pump
> These came with my ElectroAuto kit.
>
> Here's what I've found is my searching, but I don't think 12 volts will
> drive this thing. Also, is "Delay on Break" what I should be looking
> for?
>
> http://www.grainger.com/Grainger/items/4E234
>
>
> Thanks all - I've enjoyed ~300 gas free miles. And when a relay
> arrives, I'll actually have HEAT! It's a high of 1 degree today in
> Iowa AAH!!
>
> Andy
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Hi Andy, Morgan, and all,

I just finished assembling a couple vacuum pump kits, so this message is
timely.

I carry a vacuum switch, similar to what other parts vendors carry (scroll
down some to see it):

http://www.evsource.com/tls_braking_system.php

It has hysteresis as Morgan was explaining, and can be adjusted for when it
triggers back on. Mounting is easiest when it goes into one of the
reservoirs I carry, but let me know and I have all the fittings necessary to
convert it to a 3/8" hose barb.

-Ryan

On 1/19/08, Morgan LaMoore <[email protected]> wrote:
>
> Usually, people use a vacuum switch that has "hysteresis" built in -
> it turns on when the vacuum falls to 18 inHg, and doesn't turn back
> off until it rises to 22 inHg.
>
> However, a time delay relay will work, too. Yes, Delay on Break is
> what you want - that means it will run for a little while longer
> before turning off.
>
> I think we have some time delay relays in a lab at work that are
> adjustable enough to work for you and has 12VDC coils. Unless you find
> something good sooner, I'll check the maker/model number on Monday.
>
> Even though 1.5A isn't enough to control the vacuum pump, that's OK:
> you could just use the output of the time delay relay to control the
> coil of a regular relay. It adds a bit of wiring complexity and an
> extra part, but if it gets your goal, that's OK.
>
> -Morgan LaMoore
>
>


> <[email protected]> wrote:
> > >
> > > Hi gang!
> > >
> ...


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## EVDL List (Jul 27, 2007)

Guys, if you're using a Gast pump with a Square D
switch, you will set the low level for 10 mm Hg, and
the upper for about 21-22 mmHg, and it will actuate 4
times before needing to take another pull.
No timer needed.
(;-p



> --- Ryan Bohm <[email protected]> wrote:
> 
> > Hi Andy, Morgan, and all,
> >
> ...


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## EVDL List (Jul 27, 2007)

Yhis is what I've been using for over a year without a relay.
Seen to work fine & is adjustable. For $25.00 
http://www.electricvehiclesusa.com/product_p/sw-600.htm
Neal



> andy-161 wrote:
> >
> >
> > Hi gang!
> ...


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## EVDL List (Jul 27, 2007)

I have a 12vdc air compressor, it is a continuous duty, that has a 1/4" 
pipe thread inlet and outlet, I was wondering if anyone has used these for a 
vaccuum pump? It's a diaphram pump and was rated for 110 PSI, I think it 
should certainly pull a vaccuum.

thanks, Josh and Jenifer
http://evalbum.austinev.org/1477

----- Original Message ----- 
From: "Ryan Bohm" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Saturday, January 19, 2008 6:14 PM
Subject: Re: [EVDL] Brake Vacuum Pump Relay cycling - need delay timer?


> Hi Andy, Morgan, and all,
>
> I just finished assembling a couple vacuum pump kits, so this message is
> timely.
>
> I carry a vacuum switch, similar to what other parts vendors carry (scroll
> down some to see it):
>
> http://www.evsource.com/tls_braking_system.php
>
> It has hysteresis as Morgan was explaining, and can be adjusted for when 
> it
> triggers back on. Mounting is easiest when it goes into one of the
> reservoirs I carry, but let me know and I have all the fittings necessary 
> to
> convert it to a 3/8" hose barb.
>
> -Ryan
>
> On 1/19/08, Morgan LaMoore <[email protected]> wrote:
>>
>> Usually, people use a vacuum switch that has "hysteresis" built in -
>> it turns on when the vacuum falls to 18 inHg, and doesn't turn back
>> off until it rises to 22 inHg.
>>
>> However, a time delay relay will work, too. Yes, Delay on Break is
>> what you want - that means it will run for a little while longer
>> before turning off.
>>
>> I think we have some time delay relays in a lab at work that are
>> adjustable enough to work for you and has 12VDC coils. Unless you find
>> something good sooner, I'll check the maker/model number on Monday.
>>
>> Even though 1.5A isn't enough to control the vacuum pump, that's OK:
>> you could just use the output of the time delay relay to control the
>> coil of a regular relay. It adds a bit of wiring complexity and an
>> extra part, but if it gets your goal, that's OK.
>>
>> -Morgan LaMoore
>>
>>


> <[email protected]> wrote:
> >> >
> >> > Hi gang!
> >> >
> ...


----------

