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Last Updated: May 03, 2013

7 segment gear indicator

Having a gear indicator like this one is a very handy visual partner to alert us to what gear we are driving our motorcycle. Some think its un necessary, but sometimes the mind gets blank and forgotten that we are driving at the wrong gear position.

The photo shown with separate gear indicator is very common nowadays with cheap bikes, A designated number on the panel tell us the gear position, (think outside the box here)....

Why not put a seven segment display to show the current gear position.

CIRCUIT

I derived the circuit from this seven segment gear indicator. I had built the unit, but not yet incorporate it inside my panel, it is under on my project plan.



This is the circuit i'll be using on this modification and eliminate the old indicator on my panel, consisting of very cheap and few parts readily available at any electronic part store, The heart of the circuit is based on the mighty 4511 , is a BCD to 7-Segment latch/decoder/driver, that will drive the seven segment display. 





CIRCUIT DESCRIPTION

With four input that uses the logic level "1" for high and "0" for low, and by following the truth table of the 4511, we can derived what number to be display. 

TRUTH TABLE of 4511
A, B, C, D, are the input, if we need 3rd gear to be display hence, input A and B must be pulled high near the supply voltage of the 4511 while as C and D must be pulled down to ground. Looking at the diagram above, the 4 inputs have a resistor that when unconnected will pull them to VCC. By pulling a pin to ground to obtain the "0" logic level, will display the number according to the truth table.



Following my old post about gear sensor of shogun PRO, (FD125XRM) and how it works, it uses the ground to contact type. There is a contact rod with spring that is connected to chassis ground that rotates with the gear selection of the transmission. The bike mentioned is a 1 down 3 up with neutral in between the 1st gear and 2nd gear.. If the rod stops at the 1st brass circled contact near the small one, corresponds to the 1st gear and ground contact will then continue and activate the circuit inside the speedometer panel. and so on with the remaining contact.

Again think outside the box. back with the truth table, we need 3 low level and 1 high level to obtain the 1st gear, but the sensor produces only one low level the rest is floating or unconnected, The circuit above needs another modification, to revert those data, i:e: low is high and high is low. or by using binary to BCD converter IC.

For follow up soon...............

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