Ongoing project: converting CB350 tachometer to take digital input

T

timmysf

Active Member
So I've got my CB350 setup with a pretty sweet electronic ignition system that offers a tach-output wire. While I *COULD* have picked up a newer, more modern tachometer that took a digital input, the truth is.. I really like the way the stock tach looks. I think it's such a classic, defining element of the old Hondas and I didn't want to swap it out for some chintzy chromed up retro-wanna be tach.

But sure I'd love to jettison that big bulky tach cable. So I started researching my options and figuring out how I'd get this to happen.

I gutted the tach, and kept just the case, faceplate and needle.

Enter the laser cutter and some acrylic sheets.

cb350-tach-1.jpg


Some trial and error, fitting the motor driver.

cb350-tach-2.jpg


With the faceplate on top:

cb350-tach-3.jpg


Finish up assembly. Then a bunch of coding on the Arduino to drive the motor from the input.

https://www.youtube.com/watch?v=DMgwbGH8ITU
 
Pretty sweet. Hahaha, I love when people come up with stuff like this... not out of necessity but because of taste. Some people will do an amazing amount of work just to have something look/feel right. That undefinable element of quality, eh?
 
you've summed up my thoughts exactly. it was a lot more work, and effort than just buying some aftermarket tach. but theres just that intangible, irreplaceable feel of quality. makes me think of that book, 'zen and the art of motorcycle maintenance'.
 
Ha! You caught my reference. Let us know how this ends up working. I'm interested to know how exactly you got it to function
 
I just finished working out a sporadic issue where the needle wouldn't return to zero.

I also repackaged it so that the computer is now inside the tachometer housing as well, and there are just three wires to hook up. the 5V+ power, GND and the input wire for the tach signal.

I got a 12V to 5V converter that I will be installing in the electronics box. (I have more features in mind after this). The 5V converter will be supplying the power to the Arduino since I dont want to subject it to the 12-14V spikes on the bike system.

Right now I have it set up only to read a "clean" square wave, that the electronic ignition module I have is outputting. I plan to improve the code so that it can read the output from a coil negative ground. From what I've researched, that type of signal is much dirtier, and will require more filtering. But one thing at a time.

My CB350 right now is having trouble w/ the right side carb, so I'm working on sorting that out then I'll be bolting the prototype tach on it and take it out for a ride to see how it performs.
 
I know this is an old thread, but I have a couple questions:

First, which electronic ignition system are you using?

And second, what's the reason for wanting to switch from the square wave to the coil?

Thanks!
 
Hi all,

Yeah this is a old thread. I decided to check to see if there were any updates on it since I last posted. I've gotten the tach on the bike, and it largely works, but there's some signal noise coming in that I need to filter out, that wasn't entirely accounted for when I was going development on the bench.

To answer the previous post ...

1. I'm using the full ignition setup from probe engineering (http://probe-engineering-inc.myshopify.com/products/pr-350tx) - really solid setup.. replaces both the ignition and advancer (most ignition setups just replace the ignition but keep the stock advancer). The guy who created the system, Mark is very nice, responsive to questions and really knows what he's talking about.

2. The square wave is easier to read in and parse, but it only will work on bikes that have upgraded to electronic ignition with tach-output. AFAIK, many dont offer the tach-output. I asked Pamco Pete on several occasions if he offered such a output, but never got a response from him. Making it work off the negative coil pole means it'd work on any bike, regardless of the ignition system.

cheers,
-tim
 
Yes, the probe engineering unit does offer output. That is what I'm using for this current iteration of the tach.

Maybe I should be a bit more clear here. My intent was to release the code and specs openly and allow for people to contribute their improvements to it.
 
Oh, that's great. I'm looking forward to seeing the source as I'm going to delve into this a bit more myself here, soon.
 
timmysf said:
Yes, the probe engineering unit does offer output. That is what I'm using for this current iteration of the tach.

Maybe I should be a bit more clear here. My intent was to release the code and specs openly and allow for people to contribute their improvements to it.
Click to expand...

I'd enjoy that. I tinker with Arduinos in my spare time.
 
I have an 81' CB125S that has no tach. and would like to buy a decent quality aftermarket electronic tachometer w/ an analog needle to hook up to my bikes electrical system.I'll be doing an engine transplant soon from a 1983' XL200R 2 valve engine that'll bolt right in.
I'll be swapping in the entire wiring harness,coil,lights,etc. from the XL200R which is 12 volts.These bikes both come w/ oem CDi ignition.I'm curious if someone makes an aftermarket electronic tach. w/ a needle similar to yours that'll hook right up to my 83' XL200R 12 vt. system ? or would I need to modify my harness/factory CDi somehow ?
 
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