MOPED ARMY

What resolution is the time scale?

This is going to be so bitchin if you get it all worked out dude.

Resolution is whatever I want within reason, I've got a pretty long delay in there right now because if you don't, the numbers can't draw fast enough and they get all blurry, but I'm going to add a Max temp function (real simple, just if new temp is greater, save new temp to Max temp each loop) and the write to the SD card will take a couple clicks, so practically speaking probably about 20 times a second without getting into fancy timers and stuff.

When I'm on the computer one of these nights, I'll put up all the links to the parts and a wiring diagram. I was just doing a little toilet-based research and found that you need to use a resistor similar to the resistance of the thermistor at the temp you want to read for the voltage divider, to keep it in the effective range of the response curve. I don't totally understand all the mumbojumbo but I saw 4.7k instead of 100k so I'll try that and see what happens.

I would like to make/maintain a GitHub repo for stuff like this

Can I help with that

Haha length in inches of course, I was drunk as hell last night at about midnight writing all this

Recently used an adafruit board at work, one of the little round ones for teaching kids to code...they put me in charge of teaching kids. Some of them got it.

Post git repo link and I my clean it up for you.

Yo, I started a project like this years ago. You can read about it here, I never got to the next stage because I'm a dumber and couldn't figure out how to read rpms reliably to do calculations with it. We should chat. Now that we are reacquainted.

Arduino Speedo Project.

I had a github setup for my project, link in the link.

Haha yeah funny because I've been working on the CDI thing too, I was pretty close back in 2015 in Texas where I was working with uC engineers all day and they could answer all my dumb questions. I had actually gotten the timer interrupt working and the scr circuit triggering the coil but I realized that it wasn't going to work the way I was planning on doing it. I'm building a speeduino for my Subaru slash future Ford truck project, there are some real smart folks in that community and they have made some bare Bones units that could be a basis for an ignition only unit. There was also a guy on a Opel forum that built a really nice simple ignition controller that I was trying to contact. Maybe if we put together a real project he would be interested in helping.

This temp display logger was just something I need for a part that I'm designing but these M0 chips are so powerful now that it really wouldn't take much to do all the sensors you could want and still have plenty of CPU left to run a CDI, display, whatever. I don't know what the timer architecture is like on these compared to the traditional a32p stuff, but I'm sure someone has figured it out.

And yeah, for temperature sensing I'm using a K type thermocouple with a MAX6675 driver chip. It's super simple and supposedly good up to 1000°C.

https://www.amazon.com/dp/B00PVTH4MW/

If you're rolling your own sensor using an RTD, there are a whole bunch of things to consider. A four-wire measurement system is recommended for any case where accurate readings are important (to eliminate lead wire effects). The dynamic range and resolution of your ADC vs the expected min and max resistance values of the sensor are also important. Also, RTDs are only approximately linear.

This article is pretty good: https://www.te.com/usa-en/industries/sensor-solutions/insights/understanding-rtds.html (edited)

You could try a shielded plug wire; using a robust single point ground will help a lot too.

Brian, how is the thermocouple working? I was planning on hooking it up for EGT with that max6675 but I haven't got this on a bike yet to see.

I was kinda avoiding the thermocouple for 2 reasons, cost and I wanted to make this plug and play with existing trailtech plug/cht sensor. I was kinda hoping someone would have a better library with at least some kind of lookup table but this should work good.

Yeah getting the table isn't hard I can get one online or if I buy good name brand thermistors I can get it from the mfg, I just don't want to figure out how to program it to use the table.

I'm using an NTC thermistor instead of an RTD because they are cheaper and the resistance changes more significantly so you don't need a separate amplifier chip. Ultimately you only get 1023 bits from the analog input and they are spaced evenly from 0-3.3v so the challenge is getting your dv/dtemp as large as possible in the effective range you want to measure. If you want to push the range all the way out to the max of 300c that means you will have fairly poor resolution at room temp, which is fne just kinda annoying when it's jumping 20 degrees just sitting there. There are a couple tricks I can use to smooth the data, and I've also heard to use a filter cap on the circuit although that's more components I would like to avoid.

Yeah that's a good idea, the other thing I was just thinking about was maybe rather than putting in the delay, I'll actually have it write to a variable that does some kind of averaging function. Like have it write a little table with say 5-10 readings, then do a average of the table to refresh the display. Right now it just sits and does 500 counts of delay so the display has time to switch the pixels.

I bet if I'm running 3 channels and doing a 10 count average, with all that math, that will easily be as much time or more than the 500 cycle delay.

Like I said the long term plan is maybe spin a board with some of these circuits built in so the less components period, the better just for everything

I figured out an even easier way to do it, for(1-10) add sumtemp=temp +sumtemp, then divide that by 10

Then print that

Busy weekend, wow, barely had time to touch this.

Here's some of the info for people that want to play along at home:

https://www.adafruit.com/product/2796

So the basis is this adafruit feather adalogger. Out of all the flavors of arduino, i picked this one because i liked the built in SD support and the form factor matches up to a good little screen. Also I already had a 3.7v lipo battery to run it, its got native USB and quite frankly i just thought the name was clever, haha. Also its an ARM m0 chip instead of the 32u4 so its faster and has more ram and all that fun stuff.

https://www.adafruit.com/product/4650

I mated it to this screen also from Adafruit. I took a guess at it, but it actually worked out perfect for displaying 3 lines of temp. The way the characters and formating and all that worked, it was better to do 3 horizontal lines, easier to read, but i would like to eventually code some kind of bar graph or something fancy.

As an added bonus, its got a 'stemma qt' port which is just a nice lil plug and play i2c interface, i could add networked sensors or all kinds of other weird stuff later.

https://www.amazon.com/dp/B07PHK4RZ7/

These are the thermistors i'm using. They are 100k NTC thermistors known as '3950' because they have a beta coefficient of 3950. Lots of 3d printers use them, they can handle up to 300C (theoretically) and they have the largest change in resistance which is good for resolution.

oh what else, i also have a 3.7v 100ma lipo from adafruit. The feather has a built in charging circuit which is flippin' rad... eventually i can use my onboard usb charger to charge it, but i probably will get quite a few hours runtime out of this as it is.