using tactile switch to operate relay, questions

Thread Starter

bobiowa

Joined Jan 25, 2022
19
Use a Solenoid instead of Air-Pressure, it's dead-simple.
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That was my initial thought as well, however i was unable to find a solenoid strong enough to pull the rod down to do the job (it needs as im told about 3lbs of force to move it) I initially tried a starter solenoid but it required way too much amperage to start it (approx 50-60 amps initially) and that was before i even tackled the switch issue. the car rides on airbags so i have plenty of air so am going to try that route. Would be all ears though if you have a source for strong solenoids, i can see where they could be used in various projects of course then there is how to switch them on with low current
 

Thread Starter

bobiowa

Joined Jan 25, 2022
19
so use a transistor to operate relay. that ways small current through switch can simply drive transistor that turns on relay.
today you get plenty of candidates - mosfet or bipolar... or use IC such as ULN2003. this is cheap and least complicated.
Here button current is only some 10mA even though all inputs are paralleled. at the same time outputs are paralleled too and could drive even much larger relay or contactor. This option only needs one very low cost part and wiring could not be simpler. even suppression diode diode is already included.

View attachment 258800
This and LowQcab's diagram have spurred me to do a little reading (i know pretty much nothing of how this stuff works) always an area i wish i knew more of.. I went out and looked up transistor to try to understand what they are and how they work - wow lots of info. I see both examples have a transistor of some sort (again dont know how to read schematics yet) but in this example appears all legs on each side (with exception of 8 & 9) are tied together? would this be mounted i assume on a board or ? also how would one measure the current between the switch and the uln2002 and the relay and the output and the relay. Is this current sizeable via the component model or ?

Sorry, not sure if these are the appropriate questions I should be asking
 

panic mode

Joined Oct 10, 2011
2,134
you can measure current using correctly configured multimeter.
or you can read datasheet
or you can do circuit analysis.

in first case datasheet for ULN2002 states that input current of each channel when powered from 17V is about 1.5mA.
if powered by 12V, current will be slightly smaller. since 7 channels are connected in parallel that would be 7x1.5mA or about 10mA.

in second case gate current is practically zero so the only significant current is through 1k resistor.
Ohms law says I=V/R so I=12V / 1000 Ohm = 0.012 A = 12mA

For testing, this can be connected to a breadboard
1643298148421.png

But for practical use, it should be soldered onto suitable PCB.
you can design your own PCB or in this case just use one of protyping printed circuit boards like
1643298107256.png
if you are new to soldering, you may want to practice a bit and maybe use socket for the IC.
this way chip can be inserted into socked and would not be stressed by excessive heat.

beware that in electronic you must pay attention to correct orientation of parts (IC, transistor, diode) or they will not work. in fact incorrect connections are likely to cause damage. so if doing this first time, get few parts just in case.
 

panic mode

Joined Oct 10, 2011
2,134
btw not all components are breadboard friendly:
1643298645285.png

1643298572975.png

for components that are not breadboard friendly three may be adapters, usually for ICs
1643298939114.png


different type of sockets exist too:
1643298756829.png
 

Thread Starter

bobiowa

Joined Jan 25, 2022
19
so i if i had a prototype board and one ULN2002 i would solder pins 1-7 together and then solder pins 10-16 together - is this correct?
 

LowQCab

Joined Nov 6, 2012
2,052
The Solenoid that You need should have come already mounted to the Shifter from the Factory.

"" what i am doing is installing a shifter handle out of a european car ""

If the Shifter-Assembly didn't come from the Factory with a Solenoid-Locking-Mechanism,
I would recommend that You DON'T try to cobble-up one on your own.
If not done with a great deal of though and proper engineering and materials,
You could create a very hazardous situation.

There is no way that ~3-pounds of force should be required to move a simple Locking-Pin.
More like a couple of ounces, or less.

If You just really want to use the Switches for "something-cool",
use one for manual control of your TCC-Solenoid ( Torque Converter Clutch ),
the other one could select Manual vs Automatic Shifting-Modes.
( Of course, this requires a modern Electronically Controlled Transmission )

If You have Electronic-Ride-Height-Control, You could use one Button for "Up" and one for "Down".
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Thread Starter

bobiowa

Joined Jan 25, 2022
19
The Solenoid that You need should have come already mounted to the Shifter from the Factory.

"" what i am doing is installing a shifter handle out of a european car ""

If the Shifter-Assembly didn't come from the Factory with a Solenoid-Locking-Mechanism,
I would recommend that You DON'T try to cobble-up one on your own.
If not done with a great deal of though and proper engineering and materials,
You could create a very hazardous situation.

There is no way that ~3-pounds of force should be required to move a simple Locking-Pin.
More like a couple of ounces, or less.

If You just really want to use the Switches for "something-cool",
use one for manual control of your TCC-Solenoid ( Torque Converter Clutch ),
the other one could select Manual vs Automatic Shifting-Modes.
( Of course, this requires a modern Electronically Controlled Transmission )

If You have Electronic-Ride-Height-Control, You could use one Button for "Up" and one for "Down".
.
.
.
This is just the shifter handle , installed on a custom linear slide which moves the original shifter (which contains the rod). The air cylinder is moving the original rod and yes believe it or not takes 2-3lbs of force to move the pawl to disengage from park (I verified this with the shifter manufacturer) I was surprised as well. The euro shifter was all electronic (out of a late model Audi) so I suspect any solenoids they had were controlled via the computer to the transmission.. good idea on the torque converter lockup (I almost did that) but decided I wanted to be able to turn the rear camera on instead and have a box that turns lockup on/off depending on the speed I set it to.
 
Last edited:

Thread Starter

bobiowa

Joined Jan 25, 2022
19
Last edited:

LowQCab

Joined Nov 6, 2012
2,052
It's a dangerous plan to attempt to operate a Transmission "Manual-Valve" with a Pneumatic-Actuator.
Skip the Audi-Shifter since it is not designed to operate a Cable or Steel-Rod.

Even with a "semi-modern" "Electronic" Transmission, like a GM 4L60E, You still have to
manually / mechanically select, at the very least, Park, Reverse, Neutral and "Drive",
even though Gears 1-thru-4 can be selected Electronically.

You never did state what kind of Transmission You are dealing with.

What You need is probably something like a "B&M" "Hammer" Shifter.
https://www.summitracing.com/parts/bmm-80885

It has a "Bolt-On" Handle, so You can make your own Handle if you'd like,
also the Plastic-Cover is optional, what You need is the mechanism underneath.
Comes with "Park-Neutral" Starter-Inhibit-Switch, and a Reverse-Switch, and Actuator-Cable.
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bmm-80885 .jpg
 

Thread Starter

bobiowa

Joined Jan 25, 2022
19
It's a dangerous plan to attempt to operate a Transmission "Manual-Valve" with a Pneumatic-Actuator.
Skip the Audi-Shifter since it is not designed to operate a Cable or Steel-Rod.

Even with a "semi-modern" "Electronic" Transmission, like a GM 4L60E, You still have to
manually / mechanically select, at the very least, Park, Reverse, Neutral and "Drive",
even though Gears 1-thru-4 can be selected Electronically.

You never did state what kind of Transmission You are dealing with.

What You need is probably something like a "B&M" "Hammer" Shifter.
https://www.summitracing.com/parts/bmm-80885

It has a "Bolt-On" Handle, so You can make your own Handle if you'd like,
also the Plastic-Cover is optional, what You need is the mechanism underneath.
Comes with "Park-Neutral" Starter-Inhibit-Switch, and a Reverse-Switch, and Actuator-Cable.
.
.
.
View attachment 258925
What is actually happening is that the "original" shifter in the car is a Lokar shifter - it is still there (buried under the new console now) it is attached via rod ends to a different shifter post with the audi handle on top of it and the new post rides on linear bearing slides. Nothing about the original shifter mechanism has changed - it is ALL manual with the exception of using an air actuator to push the locking pawl down so it can come out of park. This is all being done (and trust me has been a ton of work to engineer / fabricate all literally for a certain "look" ) :) . I can assure you I am am a very conscientious builder/designer and keeping the locking mechanism intact on the Lokar shifter (only being actuated now via a switch) was a must. I could have very easily just removed the locking mechanism but it would have been unsafe. Oh and the trans is a 700R4
 

Thread Starter

bobiowa

Joined Jan 25, 2022
19
Well, just tested the Chinese circuit boards (showed up today) and all is well - assuming the air cylinder has the nuts to move that rod.. :)
 
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