Tach LED Bar....little different than most

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aort

New Member

• Feb 5, 2009

• #21

So you think each of the 10 pins coming off of the LM3914 could run 10 LED's? Would there need to be a transistor there? Then I could just change the voltage reference to match what 1000 RPM = in volts? So each time it got high enough (1000 RPM) the next pin would turn on the next set of LED's.

 

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picbits

Well-Known Member

• Feb 5, 2009

• #22

Each output of the LM3914 will drive 1 LED on average so you'd still need a transistor or MOSFET per output to drive a bank of 10 LEDs per output.

 

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aort

New Member

• Feb 5, 2009

• #23

Ok I have that, so the output of the F-V to the input of the LM3914 and then from those outputs to a transistor to a bank of 10 LEDs. The only thing I would need to figure out how to do is adjust it so it turns on the next bank every 1000 rpm. Is that easily done?

 

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picbits

Well-Known Member

• Feb 6, 2009

• #24

Its all in the maths from now on.

To be honest, from your questions it appears your level of electronics knowledge would make this quite a difficult starter project for you.

Worth having a play with it though as its only a few ££/$$ worth of bits.

 

A

aort

New Member

• Feb 6, 2009

• #25

I think I have everything except how to adjust where it turns on the next level.

Like I said..I usually just build whatever is specified. This is the first thing I have tried to actually build myself. Thanks for your help.

 

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picbits

Well-Known Member

• Feb 6, 2009

• #26

You can't set the individual points but you can set the start and end points and the rest inbetween are linear on the 3914.

Like I said- grab one and have a play with it,