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VRS Signal Conditioner fitting to Honda S2000 Gearbox


Ian Kinder (Bagpuss) - Joint Peak District AO
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The Honda S2000 Gearbox is fitted with a sensor which counts pulses to drive the S2000 Dashboard used in the Honda car. I wanted to use it to drive my Dash2 but I didn't want to splash out for this from RT- VRS Signal Conditioner as @SteH did. It's required because the Honda gearbox produces too many pulses per mile for the Dash2 to handle (limit is 12000 pulse per mile). The 4 bolt pick up on the front hub produces circa 3600 PPM). The Honda Gearbox produces 159002.67 pulse per mile with a 3.92 diff and 205/50/15 rear tyres. Hence the number of pulses needed dividing by 32 (which the RT item can do). Ste also discovered the 5V output level square wave from the gearbox reduces in amplitude with speedo and above 45mph didn't work. Hence he came up with a clever pull up circuit to keep the amplitude at 5V above this speed. This has been working successfully for Ste for some years.

 

I've been playing with my own pulse divider circuit and with a test gearbox (not with all the gears)  kindly loaned from @Si.Dalziel had limited success building a working item. The wife wasn't too impressed with a gearbox in my loft office, but equally didn't twig that Bagpuss still got driven with this in the house!

 

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My circuit used two counters in series to achieve the divide by 32 required-

 

 

 

image.png.301f8069658ab6aad3d0b57f8c0aa45c.png  image.png.39cb68e13f974104255010adb474aa03.png

 

I included Ste's pull up circuit on the input.

 

image.png.241de25b7b17b93dd7a81315e07bda0e.png

 

As can be seen on the trace above, sometimes output pulses would be missed. 

 

Luckily I retained the Honda S2000 harness from my build which contained the plug required for the gearbox sender.

 

image.png.94c0fab206dc0e7c0c94afb6cd958a92.png  image.png.0849b460530e1edf6cfc003085f07b48.png

 

image.png.0f97c1b4b68aaaac0ba606cd434d7f7e.png

 

I fitted my circuit to the car, but as expected, a road test showed variability in results, meaning more head scratching was required. So I've put the standard wheel pickup back into use.

 

Over the last few months, when on longer runs, my Speedo has misbehaved by either reading crazy speed values briefly like 288 MPH or dropping to zero for a period of several miles or more. The air gap has been checked, wiring checked for loose connections etc. Sensor checked for it getting hot from heat from brakes/hubs (It's generally stone cold!).

 

I was about to order a new wheel speed sensor (circa £35+VAT and Postage) when I though the VRS box isn't much more, so I had a chat with the good folk at RT and they agreed to make one with Ste's circuit built in. I also asked if they could bring out a 5V supply to feed the sensor with (and they said yes!)

 

It was quickly built, tested (Here's a pic they sent to confirm good operation)

 

image.png.edb24f9c38860e1a59da27a5706d62b7.png

 

It comes with nice length leads which are labelled too (20p is included for scale).

 

image.png.9de334524aaffa93bae1f7faeea772f9.png

 

I wired the 12V supply to the item from the 500mA fused 12V supply to my Dash2. 

 

 

It's been mounted with velcro to the top of my Arduino dash controller under the scuttle-

 

image.png.2b3a041bef66331a74634afc3a2d6a45.png

 

 

The pulses per mile (KM on the V10 firmware I'm running ) were entered into the Dash2 config tool

image.png.0e34ceaa51734471a10460d54d95548a.png

 

 

and road tested as working great compared to my TomTom GPS verified speed.

 

 

 

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p.s. If you'd like the same or similar, talk to Greg at RT as he's happy to do it again!

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Good job MrK. As we discussed, this same solution could be applied to an electronic VDO or ETA analogue needle type speedo.

 

Happy with my solution at the moment, speedo behaves ok atm. Famous last words….

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3 hours ago, Ian Kinder (Bagpuss) - Joint Peak District AO said:

p.s. If you'd like the same or similar, talk to Greg at RT as he's happy to do it again!


when my wheel speed sensor fails this will be the route I take. Just need to find a replacement plug now 🤦‍♂️

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