Home made gear indicator for AW4

[torfinn]

I have just build and fitted a home made gear indicator for the AW4 transmission, into my 89 XJ. I used two 7-segment displays. One shows the gear position 1-4 and the other shows an L to indicate Lockup. I used 4 TTL circuits 3 optocoupler, 2 7-segment displays and a few other components. I fitted it yesterday and it works very fine. It actually shift gears half a second before I notice it on the car. When breaking in 4th gear it actually shifts down to 2nd, and then up to 3rd when breaks are released.

Here are som pictures:

More pictures here:
http://www.offroad.no/snitz/topic.asp?TOPIC_ID=71978

Torfinn
89 XJ 4.0

 

[nekocopter]

Hey man, that's some nice work there.

I have just LED indicators in my dash.. But I love the enginuity.

Any plans on mass production?!

 

[5-90]

I have just build and fitted a home made gear indicator for the AW4 transmission, into my 89 XJ. I used two 7-segment displays. One shows the gear position 1-4 and the other shows an L to indicate Lockup. I used 4 TTL circuits 3 optocoupler, 2 7-segment displays and a few other components. I fitted it yesterday and it works very fine. It actually shift gears half a second before I notice it on the car. When breaking in 4th gear it actually shifts down to 2nd, and then up to 3rd when breaks are released.

Torfinn
89 XJ 4.0

Nice - have a clearer picture (or a scan) of the schematic? I can redraw it for you, and I'd like to see it for myself anyhow.

Once I see the schematic, I may be able to see about laying out a PC board as well...

 

[XJPhoenix]

That is really cool.

Kinda like a rally car!

Was it hard to do?

 

[torfinn]

It consist of the following parts:
7447 7-segment driver
74LS83 binary adder
74LS04 Inverter
74LS86 XOR gate
7805 voltage regulator
It was not very hard to do but I had to think of it a while, and did some testing in my workshop at first. THe hardest part probably was to hold the stripboard in place inside the clock housing. I glued it in place. I connected a 5 lead wire to the trans tcu under the glove box. Cut and splice the wires to the tcu.

The AW4 controls the gears by 2 solenoids in addition to a 3rd used for lockup. These are like this:

SOL1 SOL2
1st 1 0
2nd 1 1
3rd 0 1
OD 0 0

For those familiar with digital numbers see that it does not follow a logic sequence as 2 gear has the highest binary number and 4 the lowest. I added a XOR gate and an inverter to make it from 0 to 3. I then used an adder to add all the numbers with 1. Those three bits are then fed to the 7-segment driver. I also used 3 optocouplers type 4n25. They are probably not neccesary but they give some protection to the 5V circuit from the 12V circuit. The outputs from the TCU are 12V. My circuit are all 5V.

5-90 I can give you the schematics I just have to edit it a little first.

regards
Torfinn

 

[DeftwillP]

I've wanted to do this for a long time. Especially now that my wife has a digital readout on her mazda 6.

 

[brak]

is this possible in any AW4? including 97-01? i like the idea of just the simple LEDs to indicate what gear and if it's locked or not.

 

[nekocopter]

Go to awshifting.com if you're just looking for the LED type indicators, I have their complete controller, with the old style knob for the gear select.... Although I rigged the LED's up myself, I believe there are schematics on the website on how to do them yourself, or they may have a complete kit by now.

 

[mr_W]

Hi torfinn,
did you consider maybe using 74LS155 to decode 'binary' from S1/S2 and 74LS147 to encode them to BCD that 7447 can understand ? This would save you one IC, and make it easier to understand and debug. Just work around mapping between 155 and 147 to create correct display numbers..

But now when I think about it, it could be that you can eliminate LS147 and 7447 completely by driving 7seg display directly with decoded output from LS155 ?

Anyway, great idea !

 

[torfinn]

I did not think of the 74ls155 and 74ls147. I am not familiar with all the circuits in this family (74xx). I am just a hobby electronics engineer. Although I have a master degree in electrical engineering (power electrics). I have studied the two circuits you mentioned, and I think it will work.I dont think you can drive the 7 segment directly from the 155. Anyway there are always more than one solution to a problem. If I will make anotherone I probably will try these to circuits.

Torfinn

 

[mr_W]

I know about many ways to solve these kinds of problems And that is the main thing about it.. I always add more and more to design, add microcontroller, add lcd display, etc, etc.. and then don't have time to finish it I have one such protoboard that can display not only gear numbers, but also speed, rpm, mileage, but missing some spare time to get it installed.

Anyway, it is so great thing to see how people always come up with some other nice ideas !

 

[torfinn]

An even more elegant solution without a microcontroller, would be to use an eprom. I am not sure how much an eprom can be loaded. If it can drive a LED directly? If not an eprom and an oktal driver is all that is needed. Then one can also get the letter P for park.

How to measure fuel comsumtion? Can on just sum up the on-time of a fuel injector? The pulse with of it is a direct measure of present fuel comsumtion? Am I right? The fuel pressure is constant, and injectors gives a certain amount per hour (19lbs?).

Torfinn

 

[mr_W]

An even more elegant solution without a microcontroller, would be to use an eprom. I am not sure how much an eprom can be loaded. If it can drive a LED directly? If not an eprom and an oktal driver is all that is needed. Then one can also get the letter P for park.

How to measure fuel comsumtion? Can on just sum up the on-time of a fuel injector? The pulse with of it is a direct measure of present fuel comsumtion? Am I right? The fuel pressure is constant, and injectors gives a certain amount per hour (19lbs?).

Torfinn

Great idea on EPROM usage, but the price of that solution could easly beat the purpose. It will also be bulky and I doubt that it can provide enough current for 7seg led

Fuel - I have PIC code that measures pulse width on input pin with precission down to few microseconds. It would just need to be multiplied with some constant. However, I don't have enough free pins on PIC to measure all 6 injectors - and their opening time overlaps for sure.. Or maybe I'm wrong on this one ?


/EDIT/ : Can pulse width vary between injectors while in one ignition cycle ? Can be that it would be enough to just measure time on one injector, and assume that other 5 get the same pulse width ?

 

[torfinn]

Great idea on EPROM usage, but the price of that solution could easly beat the purpose. It will also be bulky and I doubt that it can provide enough current for 7seg led

Fuel - I have PIC code that measures pulse width on input pin with precission down to few microseconds. It would just need to be multiplied with some constant. However, I don't have enough free pins on PIC to measure all 6 injectors - and their opening time overlaps for sure.. Or maybe I'm wrong on this one ?


/EDIT/ : Can pulse width vary between injectors while in one ignition cycle ? Can be that it would be enough to just measure time on one injector, and assume that other 5 get the same pulse width ?

I think that pulse width wouldnt vary between injectors in one cycle. Why should it. Each cylinder should have the same fuel amount. It wouldnt make sense that an individual cylinder should have a richer fuel mixture than others. So it would be adequate to measure one cylinder and multiply with 6.
I checked the price for the eprom. The cheapest (28 pin) is around $10. approximately the same as the 4 circuits I used. Since it is only 4-5 bytes used i think one could programme it with just switches.


Torfinn

 

[mr_W]

It seems indeed that standard CMOS EPROM will be too weak to drive LEDs in this kind of display. And you see, for less than $10 you can buy PIC microcontroller which can do decoding job and drive LEDs directly. It is really cheapest solution.

Also, you will have some spare I/O pins which you can use for other interesting stuff - for example add 2 buttons, and 2 relays. Relays to control S1 and S2 solenoids, and one button for UP shift, one button for DOWN shift, and there you have tiptronic for ~$10

 

[spammermanusa2]

how would you set that up ive been realy confused how to swich gears with two momentary swiches. i just cant figure out how to do it if you could explane it in detal that would be great.

 

[mr_W]

how would you set that up ive been realy confused how to swich gears with two momentary swiches. i just cant figure out how to do it if you could explane it in detal that would be great.

Basically you need a up/down binary counter with separate 'clock' lines (switches) for counting up and down. You will also need some logic to convert binary output to aw4-encoding-type (also 2 bit, but not really compatible with what we know as binary numbers).

So you have two ways to accomplish this. using standard TTL or CMOS logic circuits from 40xx or 74xx series, OR you can use just single microncontroller (like microchip 16f84 for example) and make a simple program to do the counting and other needed stuff in software. Then you burn in this programm in microcontroller and your done.

Now, even this 'microcontroller, software, burning, etc..' sounds complicated, it is actually cheaper than buying 3-4 standard logic circuits. In addition, you can implement additional features in software as well, all for same price.

Of course, in both cases you will need some output driver transistors for relays, and relays itself.

Hope that this helps.

Btw, you can look at this thread also:

http://www.naxja.org/forum/showthread.php?t=103658&highlight=tiptronic