Easy-X
Super Spammer
Joined: 08 Mar 2019
Karma :  
|
 Posted: 22:43 - 20 Sep 2026  Post subject: |
 |
|
| stinkwheel wrote: | My suggestion would be to do without a rev counter. You don't need one. Fit a nice clock in its place. |
Quite happy to do that but Royal Enfield have made the speedo/tacho combo as a single unit with a propriety connector that drives both gauges. From what I've read, I'd have to partially recreate the circuit board that acts as base between the two.
In happier news, I've had a long conversation with Gemini and rifled through my spares boxes. I've managed to conjure up a signal generator that outputs roughly 3V peak-to-peak AC from an RP2040. The test program spits out a simulated 1000, 2000, 3000, 4000 & 5000 RPM (with the onboard RGB LED changing colour in sync, nice!) all verified with my oscilloscope. It can run from a USB power bank for testing so hopefully jabbing a couple of wires into the tacho will coax some reaction. I've also found a 12V to USB 5V converter - essentially the guts of a cigarette lighter adapter.
So that's power and output covered. For input I've got an optocoupler and some transient voltage protection components on order. Gemini assure me it's all piss easy, fingers crossed!
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
|
Easy-X
Super Spammer
Joined: 08 Mar 2019
Karma :
|
| Posted: 23:32 - 24 Sep 2026 Post subject: |
|
|
Started connecting up the final bits of the loom. The left switch cluster is again shared amongst loads of Royal Enfield models, lights and brakes work. The indicators were weird, wouldn't flash but had a dim always on look to them. I thought maybe some earthing issue as the loom wasn't fully connected but I tried a spare 2-pin flasher unit first and it worked fine. Funny how the old one was working up until now.
I have the test circuits for "fixing" the tachometer signal laid out on breadboard. Just in case anything gets knocked out of place, I knocked up a schematic in KiCad:
https://i.ibb.co/7dMg9Zf3/Screenshot-20260924-232630.png
(click to enlarge)
Starting on the TCI-unit side, there's 12V running from the kill switch and switchable negative from the TCI. Power goes through coil, TCI flips the switch, field collapses, high voltage pulse generated by the coil - standard stuff. The 2.2K resistor is so the LED in the optocoupler isn't overwhelmed by 12V and the diodes are there in case there's any back EMF.
The optocoupler output feeds GPIO8 with a pull-up resistor and a capacitor for noise. Magic happens in the RP2040 (micropython script) and re-timed pulses emerge from GPIO14. The I/O pins only spit out a lightweight DC signal so there's a BC547 transistor beefing up the 3.3V to 5V. Then a tantalum capacitor for DC blocking and hopefully 3V AC should emerge for the tacho.
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
|
Help & FAQs
Search BCF
Members
Groups
Events Calendar
rating
rating