Issue Wiring Speed Sensor For Digidash

[Guest Dean Morledge]

Hi All,

 

So the speedo doesn't seem to work on my koso digital dash possibly down to the sensor that is connected. The sensor was connected when I purchased the car into the type 9 box and appears to be an original ford sensor with 3 wires coming out of the unit up to the digi dash.

 

The sensor is pictured below

 

 

The issue I have at the minute is that there is a live feed going from the digi dash and a negative feed also going from the dash to the sensor, these have been tested on a multimeter and give a reading showing that this is working as expected.

 

The third wire on the sensor is the "pulse signal" wire which I believe should produce an electrical signal back to the dash as pulses so it can convert this info into a speed reading. The problem I am currently having is that there is no feed up the pulse wire at any point even when the sensor spins. In fact if you connect the multimeter to the ground and then the other end to the signal wire the multimeter seems to want to read negative figures.

 

I have no idea why the multimeter is showing this reading so if anyone can enlighten me as to what I am doing wrong before I go and order the official part from digitalspeedos.co.uk that is supposed to do the same job as the part currently fitted then that would be good.

 

If you need any clarification on what I have put above then let me know and I will see if I can explain it better.

 

Cheers

 

Dean

[Guest Dean Morledge]

OK so doing a bit more research..... the type 9 gearbox I have is from a later 2l granada and has the electronic speedo as standard on the box on the opposite side to the older type 9's with the mechanical speedo.

 

Most info I can find say that the sensor normally has a 12v feed to it but apparently the Koso digi dash only outputs a 5v feed - possibly an issue?

 

whoever originally fitted the sensor has changed the wiring from the sensor to the digi dash so it is possible that they have wired it up incorrectly - I will need to check this just to confirm that what is coming out of the sensor is correct to the digi dash.

 

Still no idea why the multimeter was doing what it was when connected to the sensor.

 

If all else fails need to find out if the adaptor sold by digital speedos can still be used on my type 9 box so I can get this working

[Longboarder]

The ford sensor is a Hall Effect sensor. They can be unreliable sometimes but you are right, its wired 12v, signal, 0v and it needs a gauge that is expecting a Hall effect signal. Can the Koso dash be configured 12v and hall effect.

 

Nigel

[Guest Dean Morledge]

Hi Nigel,

 

I got some info from Jon Pullara over at digital speedos which is below - it seems to suggest that the hall effect sensor can be used with the koso dash but if the sensor has to have a 12v feed then I cant see that it would work with the 5v feed of the digidash. My original thought was to connect the hall sensor with a 12v feed and use a regulator to step it down to a 5v feed but again according to the below info that could break the digi dash... looks like I could be stuck here!

 

 

Firstly let me explain to you how the KOSO speed sensor operates.

 

Internally the gauge circuit generates a 5 volt supply that in turn is converted to 5 volt pulse by

the KOSO Speed sender. You set up the wheel size and then insert the number of 5 volt pulses

it receives during each single rotation of the wheel to a maximum of 61 pulses. I.E. If the outside

diameter of the wheel is 1000 mm and it pulses 4 times the gauge recognises that every 4 pulses you

have travelled 1000 mm in distance.

 

Providing you use all three of the wires from the KOSO speed sensor there is no reason why

you cannot use a different hall effect sender providing it is a 3 wire sender, however under no

circumstances must any outside voltage or pulse be allowed to enter the gauges speed sensor

circuit – even if it is 5 volts otherwise damage will occur..

 

The wire colours in the cable are

White = Pulse,

RED = +5volt,

Black = Gauge Internal circuit ground. (Not to be confused with the gauges Black external ground

wire or the vehicles ground)

 

The other complication is the number of pulses the stock sender generates per revolution of the

wheel for instance on a Yamaha R1 motorcycle it generates 59 pulses per single revolution of the

wheel.

 

The first thing to do is to try and determine how many times the stock sender pulses it doesn’t

matter if its driven by the crank or the gearbox or the differential you are only interested in its

relationship with one single turn of the road wheels. Providing it’s under 61 pulses you should be

able to calibrate the gauge without trying to mathematically adjust the wheel size to compensate.

 

In summary it is possible to use the existing sender providing it has three wires and is only powered

by the KOSO Speed sensor circuit any outside voltage or earth will permanently damage the gauge.

 

Please contact me if I can be of any further assistance.

 

DISCLAIMER

The information above is based upon my own experience and assumptions it is not the official

KOSO line and I am not an official representative or employee of KOSO nor do I indemnify any risk

attached to the information, you are strongly advised to install the Koso speed sensor as per the

manufacturer’s instructions. This information is the sole copyright of Jon Pullara and must not be

passed on or in any way published in Magazine articles on Social Media such as Face Book Twitter,

Internet Forums or Websites.

[Longboarder]

OK so koso will read a hall effect signal. Wire it correctly to the ford sender. If the ford sender will run on 5v, is serviceable then all will be well.

Otherwise it may be simpler to go for a bolt sensor or reed switch and magnets.

 

Nigel

[Guest Dean Morledge]

That's the impression i got that it should work ok however as per my original post it didn't seem to output anything at the signal wire. Ive got to check that it is wired up correctly as per the earlier wiring info and if it is then it looks like i might be going for a magnet/sensor on the prop.

[IanS]

The Hall sensors I use at work output a short to 0V so a multimeter will not see anything connected between the 0V and signal line.

Connect the meter between the 5V feed and signal and you should see the voltage change between approx 4.3V and below 0.5V as you slowly turn the input cog.

You might need to connect a pull up resistor between the signal and 5V wires to make it work.

4.7K ohms should work and they can be got for pence from maplins.

[gncgray]

Hiya Dean

 

I to have a Koso dash and having probs with the sensor. I am using the sensor on the prop. I have glued a small piece of metal onto the prop and mounted the sensor to a bracket. I have put that I have got 1 sensor point and the diameter of the tyre but dont seem to be getting the correct speed.

 

Graham

[Guest Dean Morledge]

Hiya Dean

 

I to have a Koso dash and having probs with the sensor. I am using the sensor on the prop. I have glued a small piece of metal onto the prop and mounted the sensor to a bracket. I have put that I have got 1 sensor point and the diameter of the tyre but dont seem to be getting the correct speed.

 

Graham

 

Hi Graham,

 

I have ended up ordering a speed sensor to pick up off a piece of metal somewhere, it should be here tomorrow so I will have to try and fit it and see how I get on. Last time we had the same problem as your having with my dads Zero we had to keep amending the size of the tyre until we got a good reading compared with a sat nav. Luckily the guy at the IVA centre set it for us using the rolling road to be within the allowed limits to pass

[gncgray]

Cheers Dean.....I will keep messing about with the tyre size and see where I get with it. Sat nav is a good idear....was going to get the the wife to drive our other car at a set speed and see what I'm getting.

 

Graham