Multiplying a signal's frequency with a constant

Hello everyone,

My knowledge in electronics is very rudimentary (solder-monkey :lol, but I hope someone here can put me on track to a solution to my problem:

I want to take the digital instrument cluster from one car and install it in mine. The sender in my car sends a 5 volts square wave signal that varies in frequency with the speed of the car. The new cluster needs a 12 volts square wave signal 6.47482 times higher to display the correct speed (I already did the math...).

Simple question: what do I need to transform the one signal in the other? (something tells me the answer won't be that easy :???


Thanks in advance for any (no really, any) info on how to proceed!

Apart from detail questions of signal waveform (I assume a digital square wave for simplicity), a PLL can do it for rational frequency ratios. 13:2 would be sufficiently accurate (+ 0.3 %) I think. It can be achieved with a CD4046 PLL and additional logic. A modern solution would use a small microprocessor and do everything in software. With this method, arbitrary frequency ratios can realized.

FvM said:

Apart from detail questions of signal waveform (I assume a digital square wave for simplicity), a PLL can do it for rational frequency ratios. 13:2 would be sufficiently accurate (+ 0.3 %) I think. It can be achieved with a CD4046 PLL and additional logic. A modern solution would use a small microprocessor and do everything in software. With this method, arbitrary frequency ratios can realized.

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Yes. Feed it into a microcontroller and map the frequency to give a corresponding output at one of the ports. I think it is a programming solution you need.
Alternatively, since you claim limited knowledge, you can generate an equivalent voltage using FVC (frequency-to-voltage converter) and use its output to generate frequency using VFC (voltage-to-frequency) converter. The adjust reference you use in each case will dictate you multiplier ratio. Hope this helps.

the question is bit confusing, ill try give a very crude answer:
1. if u want to just amplify signal voltage from 5V to 12V, use comparator from 0V to 12V rail and give 2V to 4V input to inverting input as reference and signal on non inverting terminal. U will get 0V to 12V p-p square wave signal. Also, there are some buffer IC's can be used to increase voltage levels.
2. If u looking for frequency multiplier, as FvM and logicon already said, use PLL to increase frequency or 8bit MCU to measure the period using capture CCP module and then generate square wave at 50% duty cycle from another CCP by decreasing the period or in effect increasing the frequency by multiplication factor u want.
3. As logicon said, u can use 555 IC to make both voltage to frequency and frequency to voltage converter, Google it, u will get lots of circuits.

hope that helps.