Switching 52 channels with one switch

Coyoteboy · Sep 30, 2005

Is there any way, simply and cheaply, that i can find a physical switch
to swap between two wiring looms on an ECU for a car? Theres 52
individual channels (all 0-12v DC, no massive currents, some are noise
sensitive such as the knock sensor).

Any help appreciated.

John Fields · Sep 30, 2005

On 30 Sep 2005 06:12:00 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com>
wrote:

Is there any way, simply and cheaply, that i can find a physical switch
to swap between two wiring looms on an ECU for a car? Theres 52
individual channels (all 0-12v DC, no massive currents, some are noise
sensitive such as the knock sensor).

Simple, but not cheap:

http://www.electronicsurplus.com/commerce/catalog/product.jsp?product_id=76714&czuid=1128098066804

Also:

www.electroswitch.com

--
John Fields
Professional Circuit Designer

default · Sep 30, 2005

How about using some of the national semi analog cmos switches?

They have a quad SPDT and several SPST types. The "on" resistance can
be a few ohms and vary some with temperature - so they are not
suitable for low impedance loads, but can drive loads like an opamp
input.

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Coyoteboy · Oct 4, 2005

Hmmm, i liked the look of that until i saw they have an on resistance
of 300ohms, a bit much i think.

J
default wrote:

How about using some of the national semi analog cmos switches?

They have a quad SPDT and several SPST types. The "on" resistance can
be a few ohms and vary some with temperature - so they are not
suitable for low impedance loads, but can drive loads like an opamp
input.

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Coyoteboy · Oct 4, 2005

yeowch, you arent kidding on the not cheap lol. Hmm, im going to work a
less expensive way round this lol.
J

John Fields · Oct 4, 2005

On 4 Oct 2005 06:40:50 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com>
wrote:

yeowch, you arent kidding on the not cheap lol. Hmm, im going to work a
less expensive way round this lol.

---
26 cheap DPDT relays?

--
John Fields
Professional Circuit Designer

default · Oct 4, 2005

On 4 Oct 2005 06:39:40 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com>
wrote:

Hmmm, i liked the look of that until i saw they have an on resistance
of 300ohms, a bit much i think.

Yeah, I know it looks bleak - but if you're feeding a high impedance

input, what is 200-300 ohms when inputted to a amp that has a 10 meg
ohm impedance or better? You won't notice the voltage 300 ohms
drops.

I used three stages of them rated at 200 ohms into a 747 quad op amp
and there was no noticeable loss of signal voltage.

Your thinking digital - we analog designers "match the hatch" (a fly
fisherman's term - meaning you put out what they will bite - because
they are biting it already - your fly matches the current hatches of
flys)

It shouldn't be dismissed until you weigh the alternatives - perhaps a
unity gain op amp on each switch would make the resistance go away?
You know what impedance you need to match . . . I don't.
--

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Coyoteboy · Oct 4, 2005

default wrote:

On 4 Oct 2005 06:39:40 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com
wrote:

It shouldn't be dismissed until you weigh the alternatives - perhaps a
unity gain op amp on each switch would make the resistance go away?
You know what impedance you need to match . . . I don't.

Im seeing your point, however im not sure what impedance i have to
match either. I know that im swapping over engine control from one ECU
to another, i know the resistance of some of the connections are to
sensors and are in the range of 0-3K, and some are connections to coils
of unknown resistance but that could be found out, and one is the knock
sensor, tuned to about 7KHz. The main problem is that the ECU is a
slighly unknown quantity as far as components, amps etc. I really
wanted a black-box-direct switching setup - any real resistance is
going to have possible implications i cant calculate for.

Appreciate your ideas though, i'll have some more thoughts around the
idea.

J

Coyoteboy · Oct 4, 2005

you know i am thinking this might be the best option in the end LOL.
Bit bulky but at least it makes a nice simple low resistance solution.

J

default · Oct 5, 2005

On 4 Oct 2005 16:36:22 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com>
wrote:

default wrote:
On 4 Oct 2005 06:39:40 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com
wrote:

It shouldn't be dismissed until you weigh the alternatives - perhaps a
unity gain op amp on each switch would make the resistance go away?
You know what impedance you need to match . . . I don't.

Im seeing your point, however im not sure what impedance i have to
match either. I know that im swapping over engine control from one ECU
to another, i know the resistance of some of the connections are to
sensors and are in the range of 0-3K, and some are connections to coils
of unknown resistance but that could be found out, and one is the knock
sensor, tuned to about 7KHz. The main problem is that the ECU is a
slighly unknown quantity as far as components, amps etc. I really
wanted a black-box-direct switching setup - any real resistance is
going to have possible implications i cant calculate for.

Appreciate your ideas though, i'll have some more thoughts around the
idea.

J

I don't know how much hassle it is, but one option would be to insert
some resistance into each signal lead - say a 1K ohm or so. If the
ECU performs like normal, you know your analog switches won't cause a
problem.

--

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default · Oct 5, 2005

On 30 Sep 2005 06:12:00 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com>
wrote:

Is there any way, simply and cheaply, that i can find a physical switch
to swap between two wiring looms on an ECU for a car? Theres 52
individual channels (all 0-12v DC, no massive currents, some are noise
sensitive such as the knock sensor).

Any help appreciated.

Hold the phone . . . How about using switches? It would take (say)
three banks of roller arm or lever arm microswitches. Three banks
would be about four inches long each.

You could manually transfer the connections with a single lever that
would slide three bars against the switch arms compressing them and
actuating the switches.

If it needs to be under remote control, I'd use something like those
new "solenoids" that are appearing in cars. They are a motor driven
plunger with a high gear ratio and about a one inch travel. A lot of
torque . . . something most solenoids lack - and they don't require
power after switching.

A pair of extra switches in the banks could be used to limit the
travel of the plunger - like the "zero seeking" mechanism used in
windshield wipers. The switches have power applied to move plunger in
one direction or the other and it travels until it switches itself
off.

The whole switch assembly would take up about 4" X 4" X 1" excluding
actuator.

The same idea could be applied to these little 1/4" SPST snap action
board mounted "reset" switches. Two banks of 52 switches with a
mechanical either-or actuator.

My guess is the SPST switches would be cheaper ten cents versus a
dollar for a microswitch, but the mechanical actuator would be easier
with a microswitch.

--

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John Fields · Oct 5, 2005

On 4 Oct 2005 16:38:50 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com>
wrote:

you know i am thinking this might be the best option in the end LOL.
Bit bulky but at least it makes a nice simple low resistance solution.

---
Digi-Key's got an Aromat JW2SNDC12V:

http://pewa.panasonic.com/pcsd/product/pwr/pdf_cat/jw.pdf

for $2.41 each, qty 26.

--
John Fields
Professional Circuit Designer

Bob in Phx · Oct 8, 2005

I would of course, be sure that the car is turned off while switching...
going from input to no input, or partial input may cause issues (damage) to
the ecu, or the sensors (map or mas),,,, just a thought...

Bob in phx
"default" <default@defaulter.net> wrote in message
news:c6j7k11030baaatrbb3nfhq6kraki1csod@4ax.com...

On 30 Sep 2005 06:12:00 -0700, "Coyoteboy" <coyoteboyuk@hotmail.com
wrote:

Is there any way, simply and cheaply, that i can find a physical switch
to swap between two wiring looms on an ECU for a car? Theres 52
individual channels (all 0-12v DC, no massive currents, some are noise
sensitive such as the knock sensor).

Any help appreciated.

Hold the phone . . . How about using switches? It would take (say)
three banks of roller arm or lever arm microswitches. Three banks
would be about four inches long each.

You could manually transfer the connections with a single lever that
would slide three bars against the switch arms compressing them and
actuating the switches.

If it needs to be under remote control, I'd use something like those
new "solenoids" that are appearing in cars. They are a motor driven
plunger with a high gear ratio and about a one inch travel. A lot of
torque . . . something most solenoids lack - and they don't require
power after switching.

A pair of extra switches in the banks could be used to limit the
travel of the plunger - like the "zero seeking" mechanism used in
windshield wipers. The switches have power applied to move plunger in
one direction or the other and it travels until it switches itself
off.

The whole switch assembly would take up about 4" X 4" X 1" excluding
actuator.

The same idea could be applied to these little 1/4" SPST snap action
board mounted "reset" switches. Two banks of 52 switches with a
mechanical either-or actuator.

My guess is the SPST switches would be cheaper ten cents versus a
dollar for a microswitch, but the mechanical actuator would be easier
with a microswitch.

--

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Coyoteboy · Oct 10, 2005

of course, i was ahead of you there

What i have thought of tho is
leaving a large number of them connected to both ECUs, and only
switching a few vitals with relays.

J

Jayson · Oct 12, 2005

What ECU are you using? (ie. Honda P28/P72, LS-1, etc.)

Did you mean so you can switch between two ECU/PCM's or two actual
engine/car harnesses? Not sure why someone would want two seperate
engine/car harnesses.. so I'm assuming at this point you want to switch
between two ECU's.. in which case, it may be much cheaper to simply change
out a EPROM.

But, not to distract from my question.. what ECU/PCM is this?

"Coyoteboy" <coyoteboyuk@hotmail.com> wrote in message
news:1128085920.295267.11940@f14g2000cwb.googlegroups.com...

Is there any way, simply and cheaply, that i can find a physical switch
to swap between two wiring looms on an ECU for a car? Theres 52
individual channels (all 0-12v DC, no massive currents, some are noise
sensitive such as the knock sensor).

Any help appreciated.

Coyoteboy · Oct 13, 2005

Its to control the same engine with two seperate ECUs - they are Toyota
ECUs for the 3sGTE engine, ones a '91 UK ECU and the other is a '93
Japanese - Jap runs higher boost ability, advanced timing and better
fuel maps and requires higher RON fuel - hence i wanted to just switch
between them for in case i cant get to premium fuel.

J

Rich Grise · Oct 15, 2005

On Thu, 13 Oct 2005 04:52:41 -0700, Coyoteboy wrote:

Its to control the same engine with two seperate ECUs - they are Toyota
ECUs for the 3sGTE engine, ones a '91 UK ECU and the other is a '93
Japanese - Jap runs higher boost ability, advanced timing and better
fuel maps and requires higher RON fuel - hence i wanted to just switch
between them for in case i cant get to premium fuel.

Google around for "rotary switches". You can get them with an arbitrary
number of poles - you just stack up the wafers. It would be a little
unwieldy, however - howcome you can't just unplug one and plug in the
other one?

Good Luck!
Rich

Coyoteboy · Oct 15, 2005

I think a 52 pole rotary switch could be a little unwieldy indeed

but i'll check them out too. I cant just unplug and replug as the ECU
pinouts are very different. I'm currently trying to find some male and
female ends to match the ecu ports but i think they are specific to the
ECU and so i might have to resort to getting a third ECU and rippign it
apart for the connectors lol.

J

Rich Grise · Oct 16, 2005

On Sat, 15 Oct 2005 16:10:44 -0700, Coyoteboy wrote:

I think a 52 pole rotary switch could be a little unwieldy indeed
but i'll check them out too. I cant just unplug and replug as the ECU
pinouts are very different. I'm currently trying to find some male and
female ends to match the ecu ports but i think they are specific to the
ECU and so i might have to resort to getting a third ECU and rippign it
apart for the connectors lol.

Get yet another third type of connectors. If I understand you correctly,
you already have one of each harness connector to plug into each of its
respective ECUs, right?

So find any old 52-pin connector, and buy one female and two males,
and map the pins however you want to. I think you can even get male
IDC's, if that's applicable at all.

Good Luck!
Rich

Switching 52 channels with one switch

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