Porsche 914 Upgrade Project - 31 - Hacking the Fuel Gauge

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4 ай бұрын

The car is almost ready to ship over to Spain, but I looked at the dead fuel gauge and decided I couldn't leave it like that. I reverse-engineered the signals going to the fuel gauge needle and the low fuel indicator light and built an ESP32-based system with two MOSFETs that drives the gauge based on the pack voltage being broadcasted over the car's Wifi network.
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@Jake01201 4 ай бұрын

Hi Mike, Good work! Was an interesting watch. Just to clarify, in the event your HV positive cable should touch the chassis, there shouldn't be any arc or short or anything. You'll find most HV cables shielding is terminated on two sides to chassis GND which is for high voltage leak detection and emi reasons. In the event one cable is in contact, the bms and vcu should stop the contractors closing until the fault is rectified. If both positive and negative are in contact, it'll blow the fuse fairly quickly and you'll have bigger issues on your hands.

@MikesTropicalTech 4 ай бұрын

Thanks for that. I don't have a smart BMS for that, but I do have the big DC circuit breaker which hopefully will do the job of tripping quickly after a short.

@Jake01201 4 ай бұрын

@MikesTropicalTech When you say, DC Circuit Breaker, as in household? I'd typically advise against circuit breakers, if it trips while driving, you can run into a world of pain! They're also not built for the automotive environment. Always take that into consideration! Wondering if you're interested in sharing your code? I'm looking to convert some of these old gauges to electronic. I'm not proficient in cpp, only higher level languages atm. So examples / guidance would be fantastic!

@MikesTropicalTech 4 ай бұрын

@@Jake01201The DC circuit breaker was provided by the vendor with the first EV conversion I did and it's specifically designed for that use. I think I showed it in one of the DC wiring videos. Sure I'm happy to share the code as it sits right now. I'll clean it up and put it on GitHub in a while but I can send it to you now if you like. Email me at the address shown in my KZfaq home page.

@jensschroder8214 4 ай бұрын

The coil in the analog display is not just a resistance, but an induction. I would try to connect a capacitor of approximately 10µF 35V between the signal and GND. You just need a slow signal anyway. The capacitor will turn the pulses into an approximate analog voltage. The Mosfet will thank you if it doesn't always see the voltage peaks and ringing. Discharging the small capacitor will definitely work.

@MikesTropicalTech 4 ай бұрын

Thanks for the confirmation of that theory! I'll incorporate that when I build the final circuit board.

@Jake01201 4 ай бұрын

@MikesTropicalTech Good suggsstion from jen. Capacitor to GND is a great method for cleaning up the signal. We use it a lot when we PWM gauges on old school vehicles with modern standalone ecus, should work perfectly for you

@MikesTropicalTech 3 күн бұрын

I'm home now and starting on the design of the final custom board for this project. Would a standard ceramic SMD cap work for this, or should it be an electrolytic. Thanks for your advice!

@EduardCB 4 ай бұрын

Small touches can make a world of difference :) At first I was thinking that the ESP is a bit of an overkill, why would you even need the WiFi for? But then I saw that you had to use it in the end. Good job!

@jensschroder8214 4 ай бұрын

It needs WIFI to read the voltage from the system without connecting high-voltage minus and 12V minus. An ESP8266 might have done the trick, but an ESP32 is cheap too. Maybe an ESP32-C2 or C3 is dirt cheap.

@MikesTropicalTech 4 ай бұрын

I was lucky that the pack voltage was already being broadcasted by the EVTV V2 controller so I just grabbed it out of thin air! I have a lot of experience with the ESP32 on previous projects and have the development environment set up and a lot of code for it already so the whole project only took about 3 days, most of that was getting the MOSFET working properly.

@EduardCB 4 ай бұрын

@@MikesTropicalTech Yeah, if you already have a lot of experience with the ESP32 and your dev env is already set up, it makes a lot of sense to go for that instead of something even lower powered, and spend a lot of time just to get up to speed :)