Hi guys,
My bike has an issue with the speed not reading on the dash, and I've been told it's the sensor, but I want to check out all the connections before I go buying a new one. The sensor runs off the gearbox.
In the manual, it says that when the bike is moving, the reading at the sensor should be "Repeat 0 to 5 V"
I get a constant reading of 5 V, moving or not.
What should it be reading?
Do electronic speedos work off a pulse? Possibly switches between 0 and 5V, and the speed that it switches indicates the speed?
That's what I thought it might be, but I don't know enough about how they operate
I'd lend you my 'scope but my brother has it in darwin atm... if you haven't sorted it by the end of the month you can borrow it...
"In all the human societies we have ever reviewed, in every age and in every state, there has seldom if ever been a shortage of eager young males prepared to kill and die to preserve the security, comfort and prejudices of their elders, and what you call heroism is just an expression of this fact; there is never a scarcity of idiots." -The Culture
Also, constant 5v would most likely indicate a shorted sensor I'm thinking...
"In all the human societies we have ever reviewed, in every age and in every state, there has seldom if ever been a shortage of eager young males prepared to kill and die to preserve the security, comfort and prejudices of their elders, and what you call heroism is just an expression of this fact; there is never a scarcity of idiots." -The Culture
So would I be right in thinking that it sits on 0, and spikes to 5 as it turns?Once per revolution, the magnet passes by the pickup, generating a voltage in the pickup. The computer counts these voltage spikes, or pulses, and uses them to calculate blah blah blah
how sensors work - 4-20mA current loop
V=IR
5 V 250 ohm 20 mA
1 V 250 ohm 4 mA
Originally Posted by Bendito
Sorry g0zer, that lots has gone straight over my head.
Layman's terms?
I have a scope, bring the bike over if you want ben.
Scope?
from the link:Sorry g0zer, that lots has gone straight over my head.
Layman's terms?
You'll often hear things referred to as being either active
or passive. Some instruments have an active output which
includes both the control of the current in the loop as well
as provide the supply voltage. This is typically specified
as being a 4-20mA output into 10-750 Ohms, or something
similar. A passive input would be a simple resistor input that
has a voltage drop to be factored into the equation once
the supply voltage is chosen. This is typically specified as
a 4-20mA input into 10 Ohm.
what i mean is i dont know whether its active or passive so 5VDC is not necessarily definitive of the sensor state.
5VDC sounds like the control voltage to me. if its a passive loop that makes it 4-20mA at 250ohms through 1VDC-5VDC. that gives you a scaling calc in the ECU something like as per below.
Are you sure you are reading the output and not the input? ie: hte input will be the control voltage. As Kryzsdsdsfdd suggests its surprising (but not impossible if they have reverse scaling) that if the output is 5VDC but your speedo is reading 0kmh. ie: if thats true and its not reverse scaled then you have a loose wire.
I 20000 uA
WR1 -4000
WR2 16000
scaling 160
%out 100 % vr 308
vo 308 km/h
I 4000 uA
WR1 -4000
WR2 0
scaling 160
%out 0 % vr 308
vo 0 km/h
Ah yep, thought of that as soon as I asked what it was haha
g0zer, following the manual, that's the output reading.
can you physically manipulate the sensor to alter the output? ie: what is impedance across the I/O from 0% to 100%?
ie: are you sure its modulating voltage and isnt as below?
V=IR
5 V 250 ohm 20 mA
5 V 1250 ohm 4 mA
erm, not sure, haven't pulled it out yet
will go have a fiddle
this "learn by doing" stuff is fun hahaha
Now that I look at it, there's nothing I can really do to it, the only way to have it in action would be in the bike with all the gears n stuff moving
I don't really understand how it works yet, so I couldn't say but that little line from the manual would suggest voltage?
yeah ben, this is exactly what the problem was with mine...
if the sensor is okay and it's a connector somewhere, then you should get a 'pulse' reading - it's as a tooth somewhere in the Gbox run past the sensor, and it picks it up. If you're getting a constant reading - which it sounds like you are, (and i was) - then it's your sensor that's fuct, because it's not picking up any movement, and you need to replace it.
trust me, if you're getting a constant voltage it's definately your sensor and not any connector. i only just replaced mine last week, and it's as right as rain now
Cheers Sairz, by the way, I only need to lift the tank a bit to get at mine, or if I had tiny girl hands, I could just do it all through the side
oops sairz is right, they wont be using a 4-20mA loop on a gearbox proximity sensor- sorry for confusion!
anyways, so if its pumping out 5VDC its failed closed.
if you can pull the sensor (so it cannot be picking up anything) and measure impedance across the sensor, if its working it should be infinite (ie: open = not picking up anything).
Ok, cool, I've got it out, so I'll go check that now.
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