Throttle position switch

[Jack Olsen]

I'd like to attach a switch to my throttle (either at the accelerator pedal or further down the throttle path) that would allow me to have a set of three LED lights indicate throttle position -- 0-33%, 33-66% and 66-100% (or thereabouts). The LED lights would be positioned up near the rearview mirror.

I'd also like to have an LED light indicate brake on/off.

The brake seems pretty simple, but I'd appreciate any suggestions on either problem.

I want to have my in-car videos indicate speed, brake on/off, and approximate throttle position. The speed will be accomplished with a digital readout from a bicycle speedometer. It's going to be kind of a poor man's Datacam.

[k9handler]

I am by no means an electronics guy...but this would kind of work like a fuel tank sending unit?



Just a though.

[Zeke]

Why not try a spring loaded potentiometer? Go to this site:
www.corsa-inst.com and find http://www.corsa-inst.com/sensors/ls15.html
Then maybe a graduated LED. I'll see if I can find one of those for you.

Edit: I can't put my finger on one right now, but I'm talking about the kind of display from a tape recorder showing sound levels in a sequential light emitting diode. Electroninc engineers, help out here a little.

[stormcrow]

I was thinking of the same thing with the pedal but using reed switches with a magnet. You would provide 12v to one side of the reed switch and the other side would be connected to one side of the led. The other side of the led would go to ground (you need to use 12v bulbs).

Anyway, a magnet would be placed on the rod of the gas pedal at the pivot (where the rod connects to the floor assembly) or somewhere near there. The reed switches would be attached to a flat (1/4" wide)alunimum bar located so that the magnet would pass close by each one.

Space the reed switches so that when the throttle is in the 1/3 position, it would light a green led, in the 2/3 position, it would light a yellow led, and in the full throttle position it would light a red led or you could do the colors the other way(red, yellow, green). A flat strip magnet would be best to use and would sequence each light keeping them on so that at full throttle all three lights would be on.


Steve

"A Porsche does more then just go fast in a straight line"

[Zeke]

Here: http://www.elexp.com/opt_0ida.htm
We're getting closer, we'll have it built tonite. Hah!

[cstreit]

Jack,

I would spend some time with an electrical engineer on this one. Yes you could rig up a series of switches to turn them on, but I'm guessing this would end up bring pretty "kludgey" by the time you got them all mounted and wired.

If you used a potentiometer (variable resistor) there are basic chips at radioshack that could read the resistance and display them on a bar graph LED as linked above...

Then again, when you're on the track, if your not at 0% or 100%, you're not going fast enough..



An even BETTER idea would be to use a bi-metallic strip resistor as a "squeeze" resistor to measure "Pucker Factor"

[Jack Olsen]

So, one way to go would be to have two or three reed switches attached to the back of my aluminum floor board, with a bar magnet affixed to the back of the accelerator. The lower switch (nearer the hinge at the bottom of the pedal, would be actuated sooner, and the one closest to the top of the pedal would be actuated last, since the top of the pedal has a longer distance to travel.

I agree with Chris that you're almost never feathering the throttle on the track. You'd probably just want two switches: one to indicate some throttle, and the second to indicate full throttle.

Or would Radio Shack solution be easier? I have zero knowledge of electronics. And by that I mean zero. I'm going to need very specific guidance on this.

[47silver]

jack:
if you are interested i would be happy to supply you with and set it up for you a programmable controller : it has 4 universal inputs that can monitor on/off type devices (relays or pedal switches) and/or analog devices (say temperatures, pressures, and position. it also has 4 universal outputs that can turn a light on or off or drive gauges (0-100%), valves etc. i can supply a position sensor (0-100%) that would have to be fastened to your throttle cable to give a 0/100% position and i may have a red led meter that can read-out in 0/100% for throttle position, and i also have relays to drive a green and red led for brake status.

be my pleasure to design and program it for you.

gary

[Jack Olsen]

Wow. Well, Gary, what I'd like, ultimately, is a little panel, mounted either to the central AC duct or just above the rear view mirror, so that in my lap videos you could see the following:

A) Red light that comes on when brakes are applied, and

B) 2 or 3 green LEDs that indicate throttle on, full throttle, and maybe one step in between, and finally

C) The digital display from the little bicycle speedometer, which is connected to a sensor on one of the wheels, triggered by a magnet.



I'm completely open to any ideas on the best way to accomplish that. Datacam is a product that allows you to add that information directly to a video feed, so it comes up like close captioning on the the tape you record. But it's very expensive ($500-$1500), and includes a lot of bells and whistles that I don't want.

What would you need to have in order to design/program it?

[Neilk]

Jack,

You will need a backlit display for the bicycle speedometer or there is a good chance that you won't be able to read it on the video.

[cstreit]

Jack,

What's your budget on this?

What about the G-Tech Comp Pro in the field of view somwhere?

I was thinking about this as a ver poor mans data aquisition because you'd have the g-techs level meters recorded on the video tape.... (Oh, that corner was xx g's, but I know I can het y much more out of the car, so I go a little faster next time...)

This is what I've been thinking about...

[BGCarrera32]

One thing to keep in mind is that you will need a way to calibrate your unit. Does 3/4 of the way down on your accelerator pedal really mean 75% throttle applied? (It may differ from car to car, etc.) Therefore, I would go the spring loaded potentiometer route, with its own little link and cam, that can be adjusted such that the movement is correct. (Its sort of like using the link to make a high and low limit switch so the LED's illuminate properly.) I'll see if I can doodle something up and post later.

-BG

[Zendalar]

Potentiometer, zener diodes, resistors, couldn't it be done like that?

[Jack Olsen]

Chris, my budget for it is low, so that if I do buy a DL-90 datalogger at some point, I haven't thrown a lot of money down a blind alley.

Reviewing video of laps has always been useful, with the exception of not being able to see when I brake or accelerate. I don't think I need much sophistication in terms of what percentage I'm accelerating -- like you say, on a track it's generally nothing or everything. And I'm still not convinced that seeing lateral G's from so dynamic a situation has much usefulness to it, at least for me. (Great gee-whiz factor, though.)

If I could get the hot lap display into the picture, all the better.

[cstreit]

I was just alking about this with Esther this morning... Coincidence abounds...

She was also of the opinion that if I was going to spend a money, get a datalogger....

But you probably could turn around and sell the G-Tech on eBay for just a bit less than you paid for it... I'm sure there's plenty of Civic's out there that need to know...

[Don Plumley]

My quick $0.02: I wouldn't do anything with a reed switch. The one's I'm familiar with wouldn't handle the banging around, dust, etc. If there are any electronics involved at all, use some sort of hall effect switch (that's the technology that replaced the mechanical distributor rotor), you can get these at most any electronics surplus store. Here's Honeywell's info on solid state sensors (disclaimer - years ago I used to work for Micro Switch).

If you use a potentiometer, get a sealed one and not a Radio Shack cheapie. And of course, for any of the sensors, make sure that in a failure mode, they don't interfere with throttle or brake position. Last thing you need is something rolling around your pedals.

I don't have the electronics knowledge to be of circuit help (though it sounds like others are) but I can help with sensor selection, mechanical configuration and packaging.

Don

[rs911t]

Anybody play guitar? Go buy an old wah-wah pedal. It'll contain all the pieces you need to rig a potentiometer to a pedal.

[Adam]

Why not draw your thottle input readings from the TPS mounted on that 3.6? I'm sure that it would give you more variable readings than just idle/WOT etc etc.. On my old BMW 535i, the TPS offered idle/part/full throttle, so I would assume that the later Motronic EMS on the 964's 3.6 would offer more information than just the basic. The fuel/ignition timing maps would rely on as much information as was able to be gleaned from the TPS, Airflow meter et al.

[Matt Smith]

Wah Wah! that's the idea. I've got one, a gen-u-ine Cry Baby Wah.

Just imagine, Jack could be chanting

"when I stand up next to a mountain, chop it down with the edge of my hand.."

as he prepares for the next apex. (Guitar freak joke only)

[TimT]

Jack..... you already have a device that measures throttle position, the TPS, your 3.6 wouldnt fire without the TPS, crank sensor, etc.

The trick is to tap the signal from the TPS I believe it varies from 5-12 volts..

The brake thing is easy. no reed switches or mumbo jumbo, tap your brake lights through a relay to fire an LED...

The actuators are already in your car, you just have to find a way to display them on the dash.