EV Instrumentation Options

[Grimm]

In planning for my upcoming EV project and weighing costs and capabilities, I've decided to go the DIY route on my controller as well as many other parts. One of the most impressive things I've noticed about the ReVolt controller is the way that basic hardware can be improved by dozens of features and repurposed for different tasks. However, there is currently no display run by the controller itself, only real time tracking via the (admittedly awesome) RTDexplorer software by Adam. I've seen multiple people on the P&S controller thread say they don't have a computer to spare for "controller control", and I myself want to take into account that even the people who do might not have a spare Windows install to put on one.

While the bootloader provides a great way to reprogram and update the controller without a laptop constantly in the car, there is still no good way to display volts/amps/precharge countdown/etc without a computer present. As I do computer troubleshooting and get donated used and half-broken laptops on a monthly basis, it's not a big obstacle for me, but there's got to be a solution that doesn't make you check your laptop while driving.

While ideally I'd do something with a PakTraker and an EVision 2, the P&S charger and controller would be phenomenal with some kind of cheap but powerful display system (also most people who DIY a controller don't have a grand to put aside just for counting how much money they're saving in MPG XD). So, the question is how we make a cheap display that won't substantially increase the cost of the controller or charger. And I don't just mean two multimeters strapped to the dash (cough) This is the "poor man's EVision" if you will.

While I was initially thinking of making some kind of LED dot matrix (pinball machine style display) that would have turned out to be just as expensive as building your own ReVolt from scratch. A better option that is still digital, software upgradable, and naturally circular-gauge friendly is a persistence of vision display. You've probably seen one before with the little fans you can get at football games that display a message on the blades as they spin. They are very versatile as well as cheap and DIY friendly so I think we can make a small addon board that communicates via CAN bus to the controller and charger.

Possible modes might be (for a 144v pack) 130-160v with a needle in between on one half and 0-500 amps on the other, with the needle changing color to red as it gets close to the danger zones. I don't know about the legality of swapping out the speedometer for a display, so I'm assuming we leave that alone. Other possible displays that could be added would be temperature, motor RPM, SOC (nice when charging too), precharge of the capacitors (zoooo0000OOOOOP FLASH goes the gauge!) as well as text displays like errors, estimated range, software variables, individual battery status, and other fun things I haven't thought of yet.

Going even further, with a simple button setup you could change controller settings or pull up a menu of presets without the need for a computer at all. Storing this data to a usb key or accessing it through a business card web server is possible too. Let me know what you think and if you have any other displays you would like to see in an EV.

[Ryland]

I have a paktrker and have yet to see another display that I would rather have, even the fancy $1,000 displays just give you the same info, or a graph, but with a touch screen? the paktrker just works well and is simple.

[mora]

How about making addon board output voltage to existing meters in car's dashboard? One could use original fuel gauge as SOC meter and maybe tachometer too. Simple "precharging" or "ready to go" outputs for leds? One would need to tell addon board tachometer scale and high/low voltages though. Same for soc meter.

[Ryland]

Mora, a simple volt meter would work then, the fancy battery meters monitor each battery to tell you if one is lagging behind, or if the whole pack is out of balance, having this information is good because it allows you to save a battery while you still can, it also allows you to see the whole pack health.
with my paktrakr gauge I learned that I had a bad connection that was limiting my range and causing half my pack to reach a full charge while the other half was only half charged, if I had let this go my whole battery pack would have had to be replaced sooner.

[mora]

I was thinking of state-of-charge (or discharge) meter. It might be possible to tell by voltage if pack is nearing end of charge. And of course it is good to know if some cells are weaker than others. But if battery size is pre-set to software and discharge being monitored constantly wouldn't it be possible to calculate batterys current state? Or at least give an estimate of whats left.

If yes, then it might also be possible to send this info as voltage to simple meter.

[Ryland]

trouble is, over time batteries loose capacity, so you could program that in as well but then you are just making a complex system to give you a simple read out, why not get all the information at your finger tips and have a simple read out as well? at least that is how the paktrkr gauge works, the display is split in half so you can have half of it give you a real time graph of battery voltage for each and every battery so you can see how the voltage drop is for each battery as you accelerate or you can have it show you a mock fuel gauge, or a graph showing a single group of batteries, or pack voltage.
the other half of the display only gives you numbers, so you can have pack voltage there as well, or percent full (like fuel gauge only in 00%), number of amps that are being drawn (if you have the amp meter pickup) number of KW's that are being used (again, amp meter pickup) voltage of each battery in a set flashing up on the display for a few seconds and it will display temperature.
If you over charge the batteries it will give you a warning and tell you what battery is over charged, same with over discharge, if it notices one of them is to quick to charge it will also give you a warning that you should check the water level, so kind of like a fuel gauge and check engine light with a check engine light reader all in a rather small gauge.

[1-ev.com]

Would be nice to have something like this but with lower price, ha...

electricbluemotorsDOTcom/bluewindow.html

[Tired2]

I am working on a few solutions to this problem... a computer is not always the best option.

I have started an implentation for a motor controller loosely based off the Open ReVolt, but using the Parallax Propeller Microcontroller in place of the dsPic that runs the revolt. I'll explain why later on, but basically I don't want to learn PIC, and I like a LOT of things about how the Propeller works.

The most important one in this respect is its ability to output color composite video, with basic graphics support. It could easily be used to graph in "realtime", or just show status, guages, etc on an "Atari" like quality. It will also output VGA at decent resolutions... all without any external components... just a few resistors. In my controller, I may not utilize this, but it would be easy to add items like this for custom controllers.

For the OpenRevolt, I would suggest you develop an additional piece of hardware that sits on the CAN interface and spends its time drawing pretty pictures for a dash mounted LCD, either composite or VGA. Think of it like RTD Explorer implemented in about $15 of hardware, in a modular add-on system. It would talk with the BMS, Controller, etc. I'll make it if I get the time and there is interest. Add an SD Card and you get bitmap graphical splash screens!

I would also want to add a mode to reverse the display to test out some cool reflection head's up display

Touch screen support and/or hard buttons are easy to work out also for a menu driven "information center"

[Grimm]

Originally Posted by Tired2

I am working on a few solutions to this problem... a computer is not always the best option.

My thoughts exactly, computers are
A. Battery powered and inefficient for single display use, in the case of laptops which are most commonly used
B. Require old interfaces that will eventually lose support (one of the only Windows 7 bluescreens I've seen came from a usb/serial dongle)
C. Big and hot (not ideal for dashboard/glove compartment use)
D. Prone to crashing

Granted, a carputer can do a lot more if it's more closely interfaced with car audio, gps, etc. but for the purposes of controller interface it seems like a massive waste. A simple microprocessor with a little extra hardware can even take over the same functions of audio/video, maybe even with audio alerts like "Low battery!"

Originally Posted by Tired2

For the OpenRevolt, I would suggest you develop an additional piece of hardware that sits on the CAN interface and spends its time drawing pretty pictures for a dash mounted LCD, either composite or VGA. Think of it like RTD Explorer implemented in about $15 of hardware, in a modular add-on system. It would talk with the BMS, Controller, etc. I'll make it if I get the time and there is interest. Add an SD Card and you get bitmap graphical splash screens!

Touch screen support and/or hard buttons are easy to work out also for a menu driven "information center"

I'd really like to see a modular system like that, attached to the CAN bus would be even more useful as Paul comes out with new toys.

If you're looking for a cheap way to get an SD card, display, and touchscreen, a decent digital picture frame might work. I think the display would be easy to hack together and use, but the touchscreen might be harder.

[Tired2]

This is not difficult... check out the Parallax Propeller.

The hard part is getting it on the canbus, which is pretty do-able with other can-enabled devices sitting next to it and speaking serial, etc.

I hope to be back to this soon, but other projects have kept me busy recently.