Non AJS Electrical Question

[leswaller]

I am trying to set up a magnetic gear indicator which relies on getting an earth when neutral is selected, however the bike's (Kawasaki KZ440LTD) electrical neutral switch wire gives 1.5v when in neutral and 12v when in gear. I have tried an ordinary relay(contacts normally closed i.e.gear in neutral) to provide an earth and this switches the neutral light on ok, but the circuit seems to need a pulse rather than a constant earth to reset it ready for the gear change. A constant earth when in neutral prevents the gear indicator from registering the gears and then it needs to be reset by switching the ignition off and on, but the next time neutral is selected the problem returns. I know it is not the gear indicator unit as just flashing an earth connection when neutral is selected makes it work ok. Hence my search for something that will just flash the earth.
Any suggestions please?

[Tolly]

The Japanese have a different system than general, they seem to go back to front by feeding through, what we think is the earth. Try switching it the other way. By the way I'm not 100% sure on the bike electrics so be careful. Good luck.

[leswaller]

I did wonder about that myself, but as the other feed seems to be commoned with other things I don't think it would work. Have a look at this circuit diagram and see what you think

http://www.kz400.com/KZ440%20Maintananc ... iagram.jpg

[JimFitz]

Hi Les

Where are you getting the earth from to flash on the neutral switch, engine block or frame? I am thinking that the earth connection to the engine may be a little poor and the voltage difference between the engine earth and the battery earth may be enough to keep the relay coil energised if that makes sense.

Regardless, the circuit diagram shows a full earth connection via the switch to the neutral lamp which has full battery voltage on the other side. With the lamp alight in neutral you should be reading zero volts on the switch output as all of the battery voltage will be dropped across the bulb. If you are dropping some across the switch then it must be faulty or the earth it is using (the engine earth) must be faulty.

Disconnect the neutral switch and try putting a meter across the switch and engine to make sure you get close to zero ohms - if not then the switch has possibly got some engine oil in the contacts.
If the switch looks ok then put the meter between the battery and engine and again you should get close to zero ohms.

Is the switch you are fitting to show which gear you are in at any time. I cannot understand how it could work by just getting a pulse to indicate neutral as that would just give it a reset point - how would it get the other information it would need to determine gear position without say another pair of sensors on the gear pedal - one for up and one for down.

Jim

[ericblincoe]

Hi. Les, presumably the neutral switch is mounted in/on the gearbox, it switches to earth on operation, if there is still 1.5v present on the "earth" side of the indicator lamp there must be a high resistance in the circuit between the indicator lamp and earth. This is either within the neutral switch itself, the wiring to the neutral switch or the mechanical mounting of the gearbox to the frame. Your relay might need 12v to energise it but only a relatively small voltage to "hold" it in the operated position. I'd disconnect the switch and measure the resistance of the contacts when in neutral, should of course be 0 ohms.

[leswaller]

Jim & Eric
The neutral indicator switch is buried in the depths of the final drive section of the crankcase and requires fairly major surgery to get at it, so getting at this is a last resort, especially as it is working ok.
I have tapped into the lead from the neutral switch to the neutral indicator bulb on the dash, and this is where I am reading 1.05v (not 1.5v as previously put due to a typo) to frame earth when the gears are in neutral and the indicator bulb is lit. Yes I also feel that this potential is due to a poor earth through the switch.
The resistance across the switch is 1 ohm and both this and the voltage readings are the same whether using the engine or the frame as an earth.
The gear indicator I am trying to use works by using two hall effect sensors which are passed by a magnet when moving the gear lever. Whilst the bike is in gear there is 12v potential on the neutral switch lead which prevents the gear number indicator from being reset/zeroed, passing through neutral changes the 12v to theoretical zero which resets the counter.
However as there is still 1.05v on the neutral switch lead at this point, zeroing is not taking place. Applying an external earth zeros the counter but unless this earth is then removed the counter remains at zero when the gears are selected. It seems that my attempts at using a relay to achieve a genuine earth connection are unsuccessful because the gear indicator tries unsuccessfully to register a gear change fractionally before the relay contacts open, so the gear change is not registered. The 1.05v appears insufficient to 'hold' the relay as I can hear it clicking so I don't think that this is the problem. Hence my search for some method of achieving a momentary earth when neutral is selected, as I think it is a matter of timing.

[ericblincoe]

Mornin' Les, you mentioned timing as a possible cause of your problems, I think it is the standing 1.05v upsetting the electronics, (they don't like it up 'em)! And of course there will be a standing 12v (alien to the electronic counter) at that point all of the time when not in neutral. If you are sure that your relay is not holding up you could produce a clean earth by switching only the relay from the neutral switch, and the indicator lamp from one pair of its contacts, the second pair could then supply your electronics with a solid 0v. (I am assuming you have a double pole relay). If you only have one pair of contacts you could feed 0V through two blocking diodes, one for each earth feed, that would do away with both the standing 12v and the 1.05v on the counter reset connection.

[Harry44]

I've only come across hall effect sensors on ignition systems they normally have three wires from memory and one is fed with 5 volts by the ECU. It seems a complicated way of doing a gear indicator. My Wife's Suzuki just has a switch with six contacts and half a dozen wires between the display and the gear box.

[aobp11]

Les, I hope I understand the problem correctly. I suppose your indicator device is wired between +12 V and 0 V (earth). The voltage level at the reset input has to be pulled down to 0 V to force a reset. You could put 2 diodes in series in the wire from switch to reset input. The diodes together need over 1.3 V before they start to conduct so the 1.05 V across the switch is not sufficient to keep the input voltage above zero. But it could be that a sink current has to be drawn from input to earth. Then an additional resistor between input and earth might be needed. So how much current flows from input to earth when connected with just a wire (ammeter)? A proper choice of resistor might be by trial and error. When a small resistance is needed then the bike's neutral light might always glow somewhat...

W.r.t. your relay setup. The relay will return to not-energized relatively slow, even when you switch to 0 V in stead of 1.05 V. When fast decay of coil current is required a high negative blocking voltage would be needed, usually produced by induction of the coil when the current supply is suddenly interrupted. With a NO relay and some additional circuitry such could be realised in your application.

Albert

[leswaller]

Eric
Are you going to the next section meeting? if so we can discus this in more detail which will be easier than trying to type it out, But I have tried your relay options and basically it seems that if the reset is more than a pulse then moving from 1st to second via neutral does not give time for the counter to register the gear change.
Harry
These Hall effect sensors are only 2 wire and as there is no ECU on the bike, which is 36 years old, it is just the movement of a magnet past them that makes them register the gear change.
Albert
I regret that your explanation is beyond my electronics knowledge. However if you could provide me with a circuit diagram with components values I can try it out
Many thanks guys for all your efforts