Timed based variable voltage

[91 XR7]

Hello all

Heh today's topic is how to get a variable output (0-5 volts) over a period of time of about 2 hours or so? Which can be reset by an input signal?

Voltage will be either raising or decending, not 100% sure yet but I just trying to figure out if I can emulate the fuel tank sensors of a car (fuel tank pressure, vent solenoid, ect.

Also another item, I know I seen it but just can't get my brain to work, having a variable resistence trigger a device (relay or light) at a set threshold?

Thank you,
Kevin

Ps: anymore deals can be given.

 

[MikeMl]

A counter driving a DAC will generate a slow ramp. Count rate can be controlled with the counting rate (variable 555 oscillator). Counter can be reset at will.

I posted a circuit that changes state (One to Zero) on change of resistance recently. What resistance value do you want to trip at? What supply voltage? How much hysteresis? What load current?

 

[ClydeCrashKop]

a variable resistence trigger a device (relay or light) at a set threshold?

Search LM339 comparator circuits for that.

 

[91 XR7]

A counter driving a DAC will generate a slow ramp. Count rate can be controlled with the counting rate (variable 555 oscillator). Counter can be reset at will.
I posted a circuit that changes state (One to Zero) on change of resistance recently. What resistance value do you want to trip at? What supply voltage? How much hysteresis? What load current?

I'm still piecing together what truly will be needed to be done to emulate what i need, I got the basic idea but it works to draw it out. Just was wondering if there was a way

Well the second circuit i'm thinking of trying to piece together would be a circuit that will replace what i tried to get to work in another post i made before on this site. Which will use a Throttle Position Sensor Signal (0-5Volts, idle below 1 Volt) and the Coolant Temperature Signal (Still figuring out that one, just know it's @1 - 1.4Volt at running temperature)

Search LM339 comparator circuits for that.

Thank you, looked into that and that may be a good choice. For what i'm thinking of maybe just a LM393? But 339 could allow me to add extra circuit (wondering if you can use the same Signal on two inputs?

Thank you again
Kevin

 

[Mike odom]

Thank you, looked into that and that may be a good choice. For what i'm thinking of maybe just a LM393? But 339 could allow me to add extra circuit (wondering if you can use the same Signal on two inputs?

Thank you again
Kevin

depends on if you have them going into the (+) or (-) inputs, and if you have hysteresis feedback. But generally, yes, you can. You can place a 10K resistor between the signal and each input you are driving for isolation. The value depends a lot on what you are driving the comparator with (active or passive outputs) and how much hysteresis you want on your input.

 

[91 XR7]

depends on if you have them going into the (+) or (-) inputs, and if you have hysteresis feedback. But generally, yes, you can. You can place a 10K resistor between the signal and each input you are driving for isolation. The value depends a lot on what you are driving the comparator with (active or passive outputs) and how much hysteresis you want on your input.

Well Being a semi Newb i had to figure out what Hysteresis was. i think i got it. and i think on the input side there should be none, since I just want to tap into the signals that are going to the ECU so any kind of feedback may have a negative effect on how the engine works.

Well at this time i think two inputs is more then enough, then maybe going to a AND gate? that then controls a transistor that turns on a Relay. But i like the idea of being able to use one input signal over two different Comparator inputs (Ie using the coolant temp sensor for the booster pump and to trigger a separate circuit at a different trip point (Say Pump will be 192F and Second be at 230F for a warning light)

Sorry for being somewhat "dumb" in regards to these things. I've always had interested in electronics ever since i was young, but never truly dug into it deeply, and some how went the way of working on cars (Building really)

I need to find some software, Free and easy to use be great, to draw up a Schematic.

Thank you again

 

[alec_t]

I need to find some software, Free and easy to use be great, to draw up a Schematic.

I find the schematic capture function in LTspice simple and quick to use. Plus, you get a great simulator to test the schematic.

 

[91 XR7]

I find the schematic capture function in LTspice simple and quick to use. Plus, you get a great simulator to test the schematic.

LTspice is based using Linear Technology components thou. and Cross referencing is slightly fun for me Program itself seems okay, still trying to figure it all out. I think it`ll just be easier for me to draw it up with a pen and paper

 

[alec_t]

LTspice is based using Linear Technology components though

Third party libraries of component models can be added and are free downloads from the Yahoo LTspice User Group.

 

[91 XR7]

Third party libraries of component models can be added and are free downloads from the Yahoo LTspice User Group.

Okie dokie, then the search is on then.

Even thou i think i'll still like to just draw it up on paper

 

[91 XR7]

We'll I think I was able to draw up something but have no idea if it'll even come close to working

Also one of my inputs is from a TPS sensor with is as we can guess a potentiometer (5 volts one one side, ground on the other) and the other input is just a thermistor that's reference to ground ? (Hopefully that a correct term). So don't know how the adjustment for the turn on points of the comparator would be effected by that.

Kevin

 

[alec_t]

have no idea if it'll even come close to working ....... So don't know how the adjustment for the turn on points of the comparator would be effected by that.

That's where the Spice simulator will help .

 

[91 XR7]

That's where the Spice simulator will help .

Now if I knew how to get that part to work! Heck I'll be surprised if it even powered up!

This is just so new to me, specially using software and not being able to find something I can just copy