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Jacky Heshi

Adding a digital speedometer into a generic EU

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17 hours ago, Tbx Nicolas said:

Hello, based on @esajwork, I made my own speedometer/odometer  which also control MSX leds. It's not fully finished as I still use 2 arduinos for the 2 t sks because I didn't have time yet to rebuild the speedometer board for all in one.

I made it independent and used an omnipolar hall sensor to calculate time between triggers.

 

IMG_5762.JPG

I saw your original ACM mod on Facebook, even asked you some questions there! I think I have the same hall sensor as you. Where have you mounted it? Did you mount your own magnets?

 

I think you’re also controlling the LEDs, something I also plan to do to improve the brake lights using the vertical LEDs of the MSX, did you just use a transistor to switch on the power via the battery and address the LEDs using the yellow wire?

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14 hours ago, esaj said:

 If you're using the wheel USB to power your circuit, they already share a common ground through that (I doubt it would work very well even laying on the side if there wasn't some common ground).

 

Nice work! I guess you mean based on this:  

 

 

Good shout on the usb ground being the common! I’ve been powering the board via usb during development so hadn’t thought of that. Woops!

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7 hours ago, Roo Williams said:

I saw your original ACM mod on Facebook, even asked you some questions there! I think I have the same hall sensor as you. Where have you mounted it? Did you mount your own magnets?

 

I think you’re also controlling the LEDs, something I also plan to do to improve the brake lights using the vertical LEDs of the MSX, did you just use a transistor to switch on the power via the battery and address the LEDs using the yellow wire?

My ACM and msx works on the same principle for the moment. But when I have time, I want to rebuild the speedometer to control the led and triggering of the dc converter from it.

So I decided to replace the vertical leds with 144leds/meter for higher definition (23 leds instead of 15)

All is powered from a dc-dc converter so that I don't pick up any current from the motherboard (especially for the leds).

The DC converter is turned on with a IRF540 by the motherboard usb output. (If someone has cleaner and safer way tondo the job, still learning).

The hall sensor is placed inside the shell, on msx next to the motherboard (A1126LUA but other works).

The 7-segment il a 0.3", SMD, common cathode and I used white which offers a great contrast and can be seen on sunny days. (Blue was not enought)

The speedometer board handles the interface and sends by i2c the info to handle the leds (mode, on/off,...)

I used a round magnet mounted between the screws of the motor sides. About 10X5  mm I guess.

It works like a charm, I used @esajsketch for the speed as the core and built many things around. 

I'm am currently working on brake lights behind, but I don't want to make it too sensitive to avoid constantly flashing and interrupting the led animations. 

If you don't wanna go that far, you can plug your speedo on the usb, and leave the led powered by the motherboard. You will only send the data through the arduino. 

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1 hour ago, Tbx Nicolas said:

The DC converter is turned on with a IRF540 by the motherboard usb output. (If someone has cleaner and safer way tondo the job, still learning).

Power mosfet should be fine, the only thing that occurred to me is that you need more than 5V to make IRF540 or similar "fully conductive". It will start to conduct after the gate voltage (Vgs) is above something like 4-5V, but it's still in the linear region (partially conducting), and dropping voltage (ie. the "resistance" of the mosfet is higher).

shbayDw.png

 

The currents are small here (<1A, probably even <0.5A), so it's probably not that big of an issue, but you might want to take a look at some logic-level mosfets (these have much lower Vgs requirement for full conduction, specifically meant to be used with "logic-level" voltages, like 3.3V or 5V), especially if you make any changes requiring higher current draw.

Placing a small PTC-fuse or normal fuse in series before the circuit might also be a smart move, in case something goes wrong, the fuse would trigger / burn, saving the wheel USB-port (and possibly the 5V regulation before it, which might be shared as the hall-sensor power). Arduino Nano draws something like <20mA while in operation (much less in sleep-states), but the LEDs might use much more, so you need to calculate or measure the entire current draw to size the fuse accordingly.

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