Tacho options for a petrol dash?

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bigbadbob76
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Re: Tacho options for a petrol dash?

Post by bigbadbob76 »

Nice one chris.

Thanks for your coil pulse analysis Bigherb. I've never had cause to scope it before so good to have an explanation of what i'm looking at.


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CJH
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Re: Tacho options for a petrol dash?

Post by CJH »

I had a go at making a bezel to fit the switch recess and hold the screen. It's ended up a bit more recessed than I'd hoped, but that's due to the thickness of the cowling, and since the driver will see it square on it's not really an issue. Needs work to make it stay in place and to make it hold the screen securely, but it should work. Of course, getting the coil pulses to drive it, rather than just the signal generator, is needed before it's any use.

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Re: Tacho options for a petrol dash?

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I added an edge fillet to the opening. Even if I can't get the tacho or trip computer to work, I think an Arduino-based clock will be better than the blanking plate I had there before (or the hole I had before that).

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937carrera
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Re: Tacho options for a petrol dash?

Post by 937carrera »

That looks really neat. 3D printed or bought ?
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Re: Tacho options for a petrol dash?

Post by CJH »

3D printed. I've never found anything to fit that hole off-the-shelf.

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I use a frosted glass build-plate, so the first layer has a matt finish, but the filleted edges don't touch the build-plate so they have the natural shine of the PLA plastic. I may go over it with a matt or satin black spray paint.
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Re: Tacho options for a petrol dash?

Post by CJH »

I've programmed before, quite a lot in fact, but never in C, so I'm on a bit of a learning curve with the syntax. But having a project to work on is a great way to learn. I've now got a rudimentary clock.

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So far it always starts up at the same time, but I've read up on how to add buttons so that the hours, minutes and seconds can be adjusted, and I'm looking into adding a battery-backed real-time clock so that keeps time while it's powered off. Although I think it would make sense to power it from the permanent live clock feed on the dash, so that it'll only need resetting when the starter battery is disconnected. I'll see what sort of current it draw to make sure it's not going to flatten the battery any faster than the OEM clock.

I've ordered some of these too. They'll make it really simple to attach wires.

Image

Next step - make up a little bit of stripboard with a resistor and zener diode, as discussed earlier, so that I can connect up to the coil tacho wire.
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bigbadbob76
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Re: Tacho options for a petrol dash?

Post by bigbadbob76 »

Looking good Chris. :ok
I like the clock, nice and simple to read at a glance.
Shame I havn't got that space on my cowl.
Those Nano breakout boards look handy too.
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Re: Tacho options for a petrol dash?

Post by CJH »

bigbadbob76 wrote: Shame I havn't got that space on my cowl.

Part number is 251953515 - listed at VW Heritage, but out of stock. Mick at NW_VW had a job lot of these some years ago. I bought one thinking I'd be able to do something with the switch hole, but never found a use for a switch there, or a display to fit. That was in the old days though, before 3D printing :D .

I've added a real-time clock module to the Nano, so now it remembers the time when powered down. Buttons look easy to implement - I'm thinking I'll start with four- one to select hours, minutes or seconds, one to increment the selected field and one to decrement, and one to toggle between clock and tacho display (or cycle round the displays if I ever add more, such as the speedo, trip computer etc).
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937carrera
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Re: Tacho options for a petrol dash?

Post by 937carrera »

I know you are a man of ambition :)

The digital clock in later 944's have just 3 buttons and include a stopwatch type function, not that anyone uses it. This is a rare picture as the LCD still functions properly.

You could omit the "decrease" button to reduce the number of buttons, not an issue so long as it cycles through the numbers quicker the longer the button is held.

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Instructions for operation are here

http://www.944online.com/cgi-bin/yabb2/ ... 1303064927
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Re: Tacho options for a petrol dash?

Post by bigbadbob76 »

Do you really need seconds?
Just two buttons needed.
how about press one to increment hours, press the other to increment mins and both (or a third) to show RPM/Clock.
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Re: Tacho options for a petrol dash?

Post by CJH »

937carrera wrote:I know you are a man of ambition :)

The digital clock in later 944's have just 3 buttons and include a stopwatch type function, not that anyone uses it. This is a rare picture as the LCD still functions properly.

You could omit the "decrease" button to reduce the number of buttons, not an issue so long as it cycles through the numbers quicker the longer the button is held.

Interesting - yes, I could certainly do without the decrease button, but I personally find it a hassle to all the way round when you just want to decrease the number by one (like the 'hours' when British Summer Time ends. To start with the buttons will be on a separate bit of strip board, and I'll see how I go. The three 'clock' buttons might be needed on other screens, e.g. to reset the trip counter.

My car's dash has a hidden 'easter egg' 0-60 timer - great fun. It occurred to me that with a clock and a speedo pulse, I could implement that feature too: start the timer automatically the moment the speedo registers movement. Maybe I need to add a calendar as well!

bigbadbob76 wrote:Do you really need seconds?
Just two buttons needed.
how about press one to increment hours, press the other to increment mins and both (or a third) to show RPM/Clock.

That's very true - a dashboard clock doesn't need to show seconds.
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937carrera
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Re: Tacho options for a petrol dash?

Post by 937carrera »

CJH wrote:
That's very true - a dashboard clock doesn't need to show seconds.

Insufficient OCD, what happens when the time clicks over to the hour and it doesn't coincide with the beep on the radio

On a practical perspective, you're going to need the seconds when you implement the GPS feature :rofl

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Re: Tacho options for a petrol dash?

Post by CJH »

937carrera wrote:
CJH wrote:
That's very true - a dashboard clock doesn't need to show seconds.

Oh they'll be there, in the background - they just don't need to be displayed.

937carrera wrote:On a practical perspective, you're going to need the seconds when you implement the GPS feature :rofl

I'll get me coat

Hmmm. I do have a GPS module in my Arduino box. It would be a really neat way of keeping the minutes and seconds correct, so then I'd only need to worry about adjusting the hours. Current draw would be a concern with GPS, but I suppose I could put it to sleep for most of the time and only wake it up once a day, say, to steer the (minutes and) seconds. And when the vehicle's on the road the current draw isn't an issue, so I could forget all about the speedo/hall sensor approach and just display GPS speed....
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Re: Tacho options for a petrol dash?

Post by bigbadbob76 »

CJH wrote:so I could forget all about the speedo/hall sensor approach and just display GPS speed....

Sounds good.
you'd get distance, current speed, average speed, time of day, trip time.... etc etc. all from GPS.
The dash binnacle cover is plastic so you would probably get a satellite signal through it too. :D
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Re: Tacho options for a petrol dash?

Post by CJH »

Yep - I think it would add something over a speedo Hall sensor approach, as it'll give a reliable speed that doesn't need calibrating, and a reliable time. And you're right, mounted on top of one of the pods, under the binnacle cover, will be an ideal spot for the GPS antenna. So although I wrote it off earlier I think I'll move GPS up the list. Just below the digital tacho. And buttons.

Aiming to get the hardware sorted this evening so I can 'test drive' just the clock this weekend.
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