Digital Speedometer (Piggyback)

[Jack Olsen]

I'm back at it, again. I have zero electronics engineering skills, but I'd like to be able to have a large digital readout for speed that I can (hopefully) have feed off of the existing electronic speedometer sensor from my 1977 transaxle. The purpose is for in-car videos, where I want to have brake and throttle indicators, as well as a digital speed display.

It's got to be pretty simple to do, right? I mean, there's a pulse coming off of the incoming speedo line, and some sort of electronic gizmo should be able to translate that into a number on a display.

Unfortunately, to a writer, the pulse-to-display part is where all the magic comes in.

Any suggestions?

I'd also like to hear if someone has a simple way to get three lights to go off based on a signal from the 1993 throttle position sensor on my car, which sends out (I'm told) either 0, 5, or 12 volts, depending on where the pedal is. I don't even know where the thing is located.

Any help is appreciated. In-car videos could be made much more useful, with this.

[island911]

Great idea Jack.
I've considered that too, but figured someone had done this already . .. don't the 993s have a speedo in the tach. . .or is that just a trip-cmptr read-out?

A toggle between mph and kph sure would be handy. Currently, I'm putting my GPS on the dash for those trips to Canada.

[jstgermaine]

You mean something like this?

http://gauldings.com/digspeedgaug.html

[Jack Olsen]

Something like that, only with big honkin 2-inch numbers, so it's legible on a video clip, and something that can be positioned on the dash (clipped to the AC vent), rather than in one of the gauge holes.

(And less than $500 would also be a plus. )

I'm thinking Radio Shack stuff. Pulsed voltage to a display.

[jstgermaine]

OK Jack, this one is probably more but doesn't BB2 deserve this kind of technology?

http://www.scienceofspeed.com/products/interior_performance_products/NSX/HKS/

Edit: It's only $289.99 without the monitor. I am sure you could visit Radio Shack and purchase some AV cable and splice up something to feed directly into your camcorder....

Edit again: I just realized that you would lose all video of the track/run that way. So I checked some sources and for an additional $75 you could have a 7.5" LCD monitor that would plug into a system via S-Video cable and show well on your video.

[jazzbass]

Funny, I'm designing a system for my car to do something very similar. Although for mine, I want the speedo in the tach, not as an add on. My new Momo wheel obscures most of the speedo so I can't see higher than 60 mph, I've twised the speedo to read up to 100, but I don't like the look. My goal for the in-tach speedo is to try and look as OEM as possible.

My big problem now is finding the right display to fit in the bottom of the tach. One from a 986/996 would be nice, but hard to find for the kind of $$$ I want to pay.

I'm sure you can find something aftermarket, but if you don't let me know. If I find the right display and build the system, its not to difficult to build two.

[350HP930]

While it has already mentioned by island911 I was also going to suggest a GPS unit that will display speed in large numbers.

When I eventually get a laptop for permanant car use I will certainly be adding a GPS PCMIA or USB device to it.

http://www.gps-store.net/naveserforla1.html

[Victor]

My brother built me something like that but for RPM's back when he was studying electronics in Uni for less than about $12 in parts (almost 20 years ago) . So it must be possible. You just need to find the right geek.

[Victor]

Oh yeah - it sat on top of the steering column and had big red LED numbers about 2" tall.

[350HP930]

Originally posted by Victor
My brother built me something like that but for RPM's back when he was studying electronics in Uni for less than about $12 in parts (almost 20 years ago) . So it must be possible. You just need to find the right geek.

Or the right DIY site.

http://members.tripod.com/~foz11/DIY_MOD_s/Digital_Speedo/digital_speedo.html

[Victor]

350HP, - agreed, but you can't bash a DIY web site for it's lunch money afterward now can you?

[JR Indy]

Pretty easy stuff really, hardest part is deciding what type of display you want. How about a recording various inputs -- throttle, brake, RPM, Speed for later analysis?

I don't track my car, so not sure what info you would want, would be happy to design something. We have a motorsports division at work -- Delphi -- Some off the shelf stuff available.

[Tyson Schmidt]

Ideally we would like:

1. throttle position on a bar graph

2. digital speed readout

3. brake on/off (a simple light would work)

4. RPM on a bar graph

5. Live video of naked cheerleaders rooting for Jack.

[Jack Olsen]

I have a GPS, but the screen would never be visible to the camera, and I'd doubt it's particularly accurate at those speeds, when experiencing so many changes in direction.

The simplest version would be a console with three lights on it, and a 3-digit speed display. There would be one red light for 'brake on,' and two green lights, one for partial throttle, and one for full throttle (or three lights, if the TPS supports one mort position). If I could also get an RPM display into the mix, then that'd be great.

The key is real big and real simple, since it's got to be legible on the little, compressed videos that I can post on the web.

Here's an artist's conception of the simple version (without cheerleaders):

[Tyson Schmidt]

Nix the cheerleaders, Jack, and you'll lose most of your target audience. Trust me on this one.

[MotoSook]

I have been looking for a cheap digital speedo for my car lately too. A friend has one that fits in the smaller hole on the dash, but he is having problems with it. On a search for shift lights, I could have sworn I found some relatively cheap programable speedos.


So the theory would be to take the cheap speedo and re-wire the LED to a large LED set on a panel, use a contact switch to trigger a light for brake (you already have one on the car! Brake light! Or just mount another light spliced into your brake circuit), a limit switch on the throttle body/plate that will send a 4-20 mA to a meter on the "Olsen" panel. 4mA would be zero throttle and 20mA would be full throttle. I spec out large control valves that use switches to determine valve position using Westlock limit switches with 4-20mA output...I'll look into it for potential use on a throttle. I'm sure Tyson can figure out a way to mount it to the throttle or one of the pivots int he linkages.

A switch similar to the Westlock would be what you want for infinite throttle position indicator, or you can mount a few contacts on the throttle linkage that will strike a stationary stripe in the range appropriate for your throttle position (say 3 separate strips) to complete a circuit and thus energize a light . One can make it linear or radial. Linear you can mount in the tunnnel... radial, you'll have to get ont he throttle or at a pivot point.

Edit: Target audiance!?! Ain't the pretty boy married? So his target audience can't be female.....so go with the cheerleaders!

[IROC]

A friend of mine here in town has done this on his 3.6-equipped SC. He has rpm and speed readouts, I believe, that are visible in his in-car camera. Feel free to PM me if you'd like his email address.

Mike

[TerryBPP]

These are Cyberdyne guages for jegs. They are generally used on 50's hot rods so I'm not sure of the accuracy.