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Old 08-18-2010, 04:29 PM   #1 (permalink)
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Throttle position indicator circuit

I have several projects that I am working or going to be working on this idea I have had for a while. What I want to do is add a bar of LEDs to show the Throttle Position Sensor (TPS) voltage as a percent. Similar to KITT from Knight Rider KNT2000's Customs and Restoration Parts :: LED Green Gas Pedal LOL. The difference is the lights would be one the dash.

Here is what I know the TPS runs from 0-5v IIRC getting percent from voltage will not be hard as I believe it is linear but can quickly check with my scanner/programmer. I would like to have an extra LED light for each increase in TP% starting at 5,10,15,20,25,50,75,100%. So at 5% 1 LED would be lit at 10% 2 would be lit.

Unfortunately it has been some time since I worked with circuits an I'm having a little trouble figuring out how to get a 0-5v reference to turn on the lights I want. That is where I need some help/guidance.

I want to go for something more simple than a Arduino hoping I can do it with a IC or logic gate. I guess the easiest way to do this would be to use a battery tester or a fuel gauge to give the reading but I would like to have it as a light bar.

Thanks for the help and I will keep everyone posted as I start working on it.

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Old 08-18-2010, 04:54 PM   #2 (permalink)
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My $25 electric scooter had some throttle lights on it, had one chip and a couple resistors and LED. I'll dig through my clutter and see if I can get a part # off the chip.
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Old 08-18-2010, 06:17 PM   #3 (permalink)
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I don't see it now, but it was basically a quad comparator and would light up 4 leds. You could double it up for 8, but you need a voltage divider ladder with taps for each comparitor, and led resistors and LED.

When I think about it an atmega 168 chip (the heart of an arduino) would make a slightly simpler circuit. You could drive like a 20 led display with 20 low power leds, 20 led resistors and 2 voltage divider resistors connected to an analog pin. Tie it into the tps 5v source (if it doesn't complain) and thats about it.
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Last edited by dcb; 08-18-2010 at 06:25 PM..
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Old 08-19-2010, 11:22 AM   #4 (permalink)
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also just noticed the UAA170 chip, looks promising:
SCUMARI Technohobby
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Old 08-20-2010, 11:46 PM   #5 (permalink)
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This should do the job: Dot/Bar Display Driver
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Old 04-05-2013, 11:32 PM   #6 (permalink)
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Sorry to bump an old thread, but I was thinking about this today and found it through a search. I wanted to put an LED strip next to the tach, since both are useful for hypermilling to determine fuel efficiency. The Dot/Bar Display Driver from TI looks promising, but I wasn't really sure what else I would need, or how to put it all together. Is there a write-up somewhere or can somebody help direct me from step 1 to the end?

Does anybody have any ideas?

The ultragauge has these:
Absolute Throttle Position 1%
Relative Throttle Position %
Absolute Throttle Position 2 %
Command Throttle Position %
Do any of these do what I am trying to accomplish?

Thanks for the help!
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Old 08-14-2014, 04:22 PM   #7 (permalink)
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Hi guys, pumping this thread to say i will work on this.
My route will be this:
new/fun LED throttle position sensor indicator, need help... - RX7Club.com

Will post info when get it done.
Regards!
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Old 08-27-2014, 05:41 AM   #8 (permalink)
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This should do it I think. It's designed for a nominally 5V TPS.

The 1M and 330k resistors are a voltage divider to drop the TPS signal (up to 5V) to 1.25V max., for input into the LM3914. The 1M also protects the TPS signal from being altered significantly by this circuit.

The capacitors and zener diodes are for dampening any noise and dissipating any voltage spikes respectively.

Because the TPS voltage will be somewhat greater than 0V with a closed throttle and less than the 5V reference at WOT, the two 5k resistors are used. These are a voltage divider, used to set the voltages that will just avoid lighting the first LED on a closed throttle and just cause the 10th LED to light at WOT.

The current through the LEDs is set by the current flowing through the total resistance between pin 7 and ground eg. {1/1k + 1/(5k +5k)} = 1/Rt. You can adjust the brightness of the LEDs - within reason - by varying the value of the resistor in the position of the 1k.
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Old 09-03-2014, 12:30 PM   #9 (permalink)
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This circuit (^) worked perfectly when bread boarded, using both TPS and MAP voltages.

For laying out the components you could start with something like this guy's: DBBP.COM (see "Tech Tips" and "02 sensor") and extend the perf board to provide space for the filtering and signal voltage divider (1m and 330k). The connections on the board can be made with short lengths of solid core wire &/or the bent over leads of the components, rather than messing with etching Copper clad board.

(Damping - ^ - not dampening.)

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