New Project - Fancy Speedometer, etc

[Volt_Ampere]

Hi - I am starting to design a fancy add-on to my Yamaha Drive (2012):

I am going to build a digital display that will show Speed, Distance (odometer), Temperature, Time, etc. I am in the early stages on this design.
I plan to use an Arduino board to control everything. I have not decided whether to use GPS for the Time, Speed, Distance or to use the pulse tach that is on the motor for Speed and Distance and a clock chip for the time.

I don't know what the pulse rate on the pulse tach is (probably 4 or 8 pulses per rev). I also don't know that voltage the signal is that goes to the controller. I will use an Optical Coupler to grab that signal once I find out what it looks like. (My cart is in Arizona and I am in Colorado for the summer)

Any ideas will be welcome. I plan to design it before I get back to Arizona in October.

[cgtech]

5v pulses from a hall effect sensor. 4 high (or power on), 4 low (power off) per motor revolution. Probably better use some means of isolation. Also keep in mind that on many carts, the tach signal is ran inside shielded wire to insulate from interference (might not be a bad idea for yours).

[dbmachine]

If you wanna save a boat load of money try this. Does everything except temperature.

http://www.buggiesgonewild.com/gas-y...must-read.html

[Volt_Ampere]

I am doing this project for the fun and learning experience. Yes I know I could use a cheapo bicycle speedometer but there is no fun in that. I will use an optical isolator to pick up the tach signal for sure. I won't tie my electronics directly to anything except to the battery volts to monitor that. I will use a differential amp to do that to avoid ground loops. I have extensive instrumentation and control experience so I know how to do the electronics right.
I hope to eventually turn this into a BMS for a lithium conversion.
Thanks for the sensor info, cgtech! Do you happen to know the gear ratio for this cart with the high speed gears? I think it goes about 25 mph now. I just need to approximate the motor rpm / mph to get started with the design of the counting system. I will set up the speedometer to work from 1 to 30 mph. I would like to do some sort of analog display but I will probably start with a digital display during development.

More ideas welcome!!!

[cgtech]

The only hs gear set available for team axle is 8:1. I have never counted the teeth to be sure it is exactally 8.000:1 (i doubt it is).

[Volt_Ampere]

Thanks. I don't need exact ratio - just something close to get started. I will calibrate it on the cart anyway. During debug I will use a pulse generator to simulate the motor pulses. I just want to estimate the motor rpm vs mph to get started with the design.

[timmyjane]

Did this project get finished?

[Volt_Ampere]

Yes and no. I have the electronics mounted and the display has Battery volts / current, State of Charge, Outside temp, Motor temp, Date, Time, and MPH. I used the motor sensor for my speedometer input with an optical coupler to isolate it from the controller electronics. That works great. I still have some programming to do to get my Odometer function working. I would like to find a better display for the speedometer. I am using a 4 line by 20 char LCD display but it's not that easy to see while driving.
I used an Arduino Pro Mini for the processor. Nice little board for under $10. The rest of the stuff I built myself. The electronics are on top of my 14 cell Lithium pack and the display is mounted up front with a beeper for low battery alarm and two buttons to change the display functions. I may try to make the display show MPH In big block letters as a display option if I can't find a better display.
I calibrated the speedometer by measuring how far the cart moved for one turn of the wheel and counted how many pulses I got for one turn of the wheel to verify the gear ratio. It agrees well with my speedometer app on my phone.
I will try to post some pix soon. I have them on my camera.

[timmyjane]

So the no part is only the display really. I guess the problem with the odometer is getting the data into EPROM to store the info after the power is off? Sounds pretty great. Would you mind sharing the parts list and code? I am working on a project that monitors the individual battery voltage and would like to integrate more information. Thanks.

[Volt_Ampere]

I am also adding individual battery voltage monitoring and balancing for my 14 cell Lithium pack. It's a work in progress. Accurate monitoring of the cell voltages is tricky. Has to be precise to do balancing. I also don't want much battery drain when it's connected and the cart is not in use.
My current improvement that I am working on is the display. I am going to program the 4 x 20 display to display large numbers for the speedometer so that I can easily see it while driving.
Yes - the Odometer requires saving the distance traveled (count of encoder pulses scaled by a calibration factor) in EEPROM. I have a separate EEPROM on my board for that but as you probably know, writing to EEPROM is a PIA. You can't write to a single location too many times without wearing it out so you have to be creative. Since my board does now know when it will be powered down, it has to save the distance traveled frequently. That is sort of low priority on my list right now.

PM Me with your real Email address and I will send you what I have - It's not intended for public consumption.