Need help--->Voltage sensing, then sendng circuit

[adodd]

Hey there, new to this forum. I am tryng to build a circuit and need some help. Hopefully I will give a decent description here. I'm looking to build a circuit where a voltage (anywhee from 0-3V) is sensed, then the voltage level can be stored, and then outputted at a push of a button. This all has to do with hooking it up to a truck's throttle position sensor. I need to read the throttle position, then mimic it without actually using the throttle.

So what I will do is step on the gas, hit a button to store the voltage spit out by the throttle position sensor, then later, hit a button to output that voltage again. Was that a good description. Anyway if anyone has some ideas, let me know. Something microcontroller based??? Or shift register???

 

[Russlk]

An analog to digital converter (ADC) and latch will save the value, then a digital to analog converter (DAC) can output the voltage. You would not necessarily need a microcontroller, but one could have the ADC built in.

An analog sample and hold circuit could be used if the time between input and output was short enuf.

 

[Optikon]

Or.... depending on how long you need the value stored (you didn't indicate), you might get away with a sample & hold type circuit and simple switches. It would be much simpler to implement than a uC or data converter.. but like I said, if you need to reproduce your voltage next week or something, you'll need digital storage.

Doh! Saw russlk already mentioned the S&H after I posted... anyways a large capacitor could feasibly store your voltage for minutes / hours if that helps you choose which way to go.

 

[adodd]

What I was thinking was to have an 8 bit A/D, then a latch or register, then an 8 bit D/A. Just not sure how to do the latching or registering. Any tips?

 

[Optikon]

What I was thinking was to have an 8 bit A/D, then a latch or register, then an 8 bit D/A. Just not sure how to do the latching or registering. Any tips?

Well, yes we have tips on this.. But keep in mind all the electronic "baggage" you'll have to design to support such a system.

A/D & D/A need clocks. Clocks need a frequency source like a crystal oscillator or similar. Depending on the A/D & D/A you pick, you may have to adhere to a protocol for the communication to the device such as I2C, SPI or similar - if this is the case, you need some other devices that can do that like a pic (and a pic needs programming, do you have one of those? can you code it?) If you pick parallel load, you still need registers & logic to control them.

You have not revealed any information about how long you really need to store & reproduce the voltage so I guess the simpler circuits are out of the question? The A/D & D/A method can surely work but is it clear what all that entails? Are you willing to find out & try it?

You will get much better "tips" & help if you can clearly spell out what you need.

1) What is max / min voltage needed?
2) how long must said voltage be stored for (worst case)?
3) What is the voltage driving when you reproduce it? Is it high impedance / low impedance load?
4) What power supplies are available?
5) any other concerns like noisy signals? need good reproduction accuracy (how good?) etc....
6) do you have a month or more to get it working (what time frame)?
7) how much $$$ can you spend?

Just some things to think about.. answers to these help the readers on this forum make th ebest suggestions to you if that's what you are looking for.

As always, half the battle is just communicating clearly what you need to do, the rest is details.

 

[Russlk]

I designed this to store a voltage long term and output in analog. No clock needed. I think it works, but I never built it.