kiker14

iTrader: (1)

hey guys, I was sitting in my networking class today, and instead of paying attention, I was thinking about fun stuff I could do with my RX-7 (this is a normal occurance). Anywho, I want to put a line of LED's (light emitting diodes, not the crystal display) that shows how much throttle I am giving the car. I got this idea from watching racing on tv and in video games where they have the little indecator of how much throttle they are giving the car. I have a gsl-se, so I figured I need to tap into the throttle position sensor or something like that. If anybody has ever done this, or knows how to, I would greatly appreciate it. Thanks!!

Unsupa

iTrader: (2)

i saw one of those on the drift bible dvd..

kiker14

iTrader: (1)

never seen the dvd.

i plan on playing around w/this soon tho, so any help would be really appreciated. I'm reading up on how TPS's work in general, it seems as if I can just tap into whichever wire goes into the ecu, hook it up to some relays, and then to the LED's... does that sound about right to you guys?

(still a newby to electrical stuff, and I don't wanna fry anything)

Jeff20B

iTrader: (13)

I think the TPS on a GSL-SE is more a switch while the TPS on an FD is more of a potentiometer. I'm sure others will be along shortly to explain the differences and correct me if I'm wrong.

Gregs

hmm sounds like an interesting idea, if you do accomplish this please create a write up and post pics

gsl-se addict

iTrader: (3)

Sure, you can make something like that. Take a look at this web page, it will give you the idea on how to wire it up.

http://dan.pfeiffer.net/train/vmeter.htm



You will have to check the data sheet for the 3916 chip to make sure that it can be powered off of 12v. If it needs something smaller, you could use a regulator. Maybe add a heatsink since this website says that the chip disipates a lot of heat when it is in the bar graph mode.

Just tap the TPS wire where it enters the ECU (pin 'I', Brown wire). The TPS will put out a max of 5V, the min is about 1V.

The only problem is that the TPS disengages from the throttle at 50% or so throttle, so your display will only indicate up to around half throttle. If you really want it to go from 0% to 100% throttle, you will need to adapt a TPS from another car that will go 0% to 100% linearly. This TPS would have to be added in addition to keeping the stock TPS. The new TPS would just be used for your display.

Hope this helps. Good luck. Electronics projects like these are always fun.

Kent

edit: Here is the data sheet for the chip. It has a lot of cool ideas on how you could make this work.

http://www.national.com/ds/LM/LM3916.pdf

kiker14

iTrader: (1)

I just went out there, found that at the TPS (I probed into the connector just off of the tps from the back side so i could keep it pluged in) when I pulled up on the throttle, it went from 1V to 5V linearly... I am by myself so I figured pressing on the petal itself wouldn't change this... how does the TPS disengage?

DAVID GRIMES

IMHO sounds like a lot of trouble for something you already kinda know.

To save money: Why not just measure the travel of your gas pedal (say 3"), paint that distance on the end of a string ( with fluorescent paint so you can see it at night ), divide by 10 and make 10% throttle marks on the string every .3", screw an eye bolt into your dash just to the right of the steering wheel, run the string through the eye ( align the start of the color with the eye ), and hang a weight to end. You'll be able to tell at a glance the percentage of throttle remaining.

Just kidding, but I couldn't resist that

gsl-se addict

iTrader: (3)

What I meant is that above 50% or so throttle, you will notice that the plunger of the TPS no longer contacts the throttle. So I you open the throttle beyond this then you still get the 5v reading. Because of this, at higher throttle you will not be able to distinguish between say 75% throttle and 100% throttle unless you get another TPS and mount it in a way that it covers the full range of the throttle movement.

kiker14

iTrader: (1)

oooooooooooo, gotcha.

that blows.

nevarmore

Utilizing the circuit from gsl-se addict, you should be able to adapt a potentiometer to hook onto your throttle linkage. Try Mouser or PartsExpress, they should have something that might work.

Its there so you can tell your passenger "That was only half-throttle," and be able to prove it.

kiker14

iTrader: (1)

OK, so, i went to radio shack. no 2916 chip. so, i bought what looked to me to be the next closest thing.

radio shack model number324. Here is a picture of all that I bought: (I also got the 276-081 20 pin bar graph display, kinda cool.

So now how in the world do I wire this all up, can it even be done with the quad OP amp i bought?

kiker14

iTrader: (1)

i don't think it can be done with what i bought.

::sigh:: looks like i'll have to order that little chip thingie.

gsl-se addict

iTrader: (3)

Yea,

You won't really be able to do what you want with the quad op-amp, unless you want only want 4 of the lights on the bar graph to light up. You will need the LM3916 chip. You will probably want to use two of them so you can cascade them as shown in the data sheet so that you can use all 20 segments of your bar graph instead of the limit of 10 with a single chip. There is a place in town here that may have them. I could go check within the next day or 2 for you. If they don't have them, I probably will be doing DigiKey order in the next couple of weeks and could add a couple of the chips on the order for you. I only need 1 little transistor, but I don't want to pay $10 or so for shipping so I need to figure out what else I may need before I order.

Kent

84stock

iTrader: (5)

First , drill a hole in the firewall. Next, run a tube up from in front of the car to the said hole. Now put on your sandals, when the air tickles your toes you are going fast, and no lights to watch.

RotorMotorDriver

iTrader: (1)

Thats great! Although I agree with what nevarmore said about the half throttle thing, my friends used to ask me all the time when I would pass a car, or jump on it getting on the highway if I was flooring it, and I never was. It was more like 3/4 throttle just to get there quick. I loved the sound of my Weber and RB exhaust together when downshifting and passing someone! However, I suppose it wouldnt really apply to my old car anyway being carbed and all, lol.

~T.J.