My (secondary) digital dash

[Map63Vette]

So this could probably go in several forums, but I'll toss it here since the Hemi swap is what ultimately drove me to it. For the quick version of the background story, I swapped a 5.7 Hemi a few years back in my 67 Dart. Originally went with a carb (didn't get computer and harness with engine, so it was the cheaper route) but have since swapped to a Megasquirt 2 Extra when I found one for a good deal.

I've debated the idea of some kind of car computer on and off for many months, but never would pull the trigger either way. Originally I wanted a Windows based computer to have the full TunerStudio functionality of tuning and monitoring, but it was going to be a few hundred bucks in the end and ultimately I don't drive the car enough to justify that cost. They had monitoring and logging software for Android at the time as well (ShadowLogger and ShadowDash more recently), but they lacked tuning support which, while I wouldn't use all the time, would be nice for any on-the-fly fix I might need. More recently MSDroid stepped up which allows monitoring and tuning on an Android system, so I looked into radios with flip out screens that ran Android, but most emulated it and didn't talk over Bluetooth very well, not to mention I didn't want to hack up my dash to fit a double DIN as flip out screens are getting harder and harder to find.

I then found my answer in the form of budget tablets. A coworker got a Dragon Touch brand 10 inch tablet to use as a depth/fish finder for his boat. I had just recently seem them as well, but didn't want something that big. Saw they had a few 7" models which were perfect for what I need. Got one with WiFi, Bluetooth, and GPS that runs Android and mounted it under my dash to use as a secondary gauge cluster. Made a quick hinge style mount on my 3D printer and took it out for a test drive the other day. Screen is super bright, even on lower settings and has a nice large viewing angle, so it's easy to read from the driving position. I need to work up some more permanent power cable options and maybe some audio output as well to work as a media library, but so far I'm really happy with it. An intrepid person might even consider replacing a dash with one, though the power cycle control might take some tweaking to get it to come on, stay on, and go off when required. The model I got was the Dragon Touch M7 off of Amazon. For only $50-60 I figured it was worth the gamble. You can modify the gauges displayed and even add your own backgrounds, but I haven't gone too far with it yet. The gauge options are a little limited right now, but it sounds like that will be expanding soon.

 

[cu440da]

Nice. I did something similar with my Warlock. I found out that the Nexus tablets (among a very few others) are GPS enabled without having to use a data plan. I needed GPS speed because my T56 has an electronic sender, the rest of the gauges I pull off my OBD port with the Torque app. Need to fab some kind of semi permanent mount- for now I just prop it up on the dash pad when I need it.

I am considering a Dakota Digital electronic to mechanical speedo converter, but they are ridiculously expensive. $300, but thats the only factory gauge that is not functioning after the swap so I might bite the bullet and do it to ditch the tablet.

 

[Map63Vette]

That's pretty much the exact same boat I'm in. The Cable X will also do electronic to mechanical conversion, but is the same price with mixed reviews. I'm trying to build something like it myself as I had some old microcontrollers sitting around from college. The sad part is I've probably spent $200 on trying to make it work so far (been through about 3 or 4 ideas by now), but the latest design only costs maybe $20 or something like that.

For the longer story I started off by trying to attached a motor directly to the input on the back of the speedo, but it didn't have enough low rpm torque to register low speeds and it needed a perfectly aligned coupling to function consistently, which would never stay that way with road vibration. Next I tried stripping a modern gauge and trying to attach the air core driver from it to the factory needle. For whatever reason the IC I bought to run the air core I could never get to work. I could use the one that came from the speedo I gutted, but I couldn't get it to scale correctly. It would be right at one speed, but low under that and high over it. I also gutted the odometer stepper motor and attached it to the factory odometer gears. It worked on a bench, but didn't work in the car so well (I think I mixed up some wires). My most recent endeavor has been to mount a small motor inside the cluster with the shaft facing out the back. I have a pulley on it and the speedo input with a belt (rubber band right now) between them. This lets me tune pulley sizes (3D printer) to get the ratio correct with a simple frequency to voltage chip to drive the motor. The main issue with little motors is they only like to turn high rpm, so the pulley lets me step it down to something usable. It works okay and this method retains the factory odometer operation. I just haven't pulled my cluster to try it in the car yet. I have a spare speedo that I've been bench testing it with.