I need a simple voltage clamp, might not be the right term, for a 5 to 0 v signal. I want to keep it from going below an adjustable point around .6 v dc

Im not the best with this stuff but ive got the diagram for a 0-5 clamp.

Project has regulated 5v input.would love to do this electrically than limiting the pot manualy.

Thanks for any help

 

Are you talking about a clamp-style electrical meter like this?
http://www.myflukestore.com/p1245/fl...FS8OOgod4RkA3Q

 

No, more like an over boost protector for map sensor turbo cars that get close to fuel cut. only i need to keep the signal from dropping below around .6 ish instead of keeping it below 4.7. like i said im horrible with electronics building and terms. most map sensors are 0-5 v were my project is 5-0 with getting below .3v causes issues, I could put a stop screw on the pot but would rather not as its not as precise in the long run.

 

You need what's called a diode clamp. It's called a 'clamper circuit' so your voltage can't drop below whatever value the diode it made for.

http://en.wikipedia.org/wiki/Clamper_(electronics)

I'll let you shop around so you can look for exactly what you need. I hope this helps.

 

Thanks, reading away

 

Im probebly not understanding the majority of all that. but it seems most of it is geared toward rectifying ac into a dc signal or keeping it from going to high. i wonder if i could reduce the regulated 5v with a pot to my low voltage with a diode and run it to the ..load? shouldnt it keep a signal even if the main pot is dropping the v lower? would adding .4-.6 v like that change the signal?

is this a bad idea?

 

If you can`t explain just what you want to do it is a bad idea.

Just what are you trying to do??

If something needs to see a voltage within a certain range it is most often for a reason.

as voltage changes different things change .

run a parallel circuit supplying your .6VDC to where you need it.

Without knowing what your doing it is impossible to know what might work.

 

I gave myself a headache rereading the wiki pages. I'd still like to figure it out but I think I'll just stop it mechanically. New bracket a tap should work. Thanks for the help guys

 

Diodes keep voltage above a certain level. Think of them as a check valve for an electrical circuit. The voltage can only travel one way. Resistors keep the voltage below a set value. If you have a 12V DC supply and you want to keep it constant at 3V you would put in a resistor. A pot (potentiometer) is nothing more than a variable resistor like the knob for your stove-top burner.

In order to find out what size resistor you need to drop your voltage down to whatever value you want it to be you'll need to know the amperage usage of whatever you're supplying the power to....your load. If the amp usage of your load is 2.5A and you have a 12V supply, your wattage is 30W. Wattage is an important number. It will not change. Now, use Ohm's Law to find the resistance of that circuit. You should come up with 4.8 ohms. Now, use Ohm's Law again, but replace the 12V with whatever voltage you need....say 3V. 3V divided by 2.5A=1.2 ohms. Subtract 1.2 from 4.8 to come up with the ohms value of the resistor you need to add into the ciruit. That will change the voltage to your load. So long as your load is rated to work on that voltage it will still use the same amperage.

I don't know how to find the value for what size diode you need.

I'm not sure if this helps or only makes things more difficult.

 

what im working in is the factory AFM. It swings from 5v down to .38 at full throttle/rpm, my truck pigs out at rpm. so i want to stop the ecm from seeing below .6 or so, preferably adjustable to dial in the cap, to limit the top end fuel. engine is none stock so its not some sensor out of whack.

i have no idea what the afm uses for ma but it really cant be much at all. Mostly im just trying not to piss of my cat when climbing a dune. a supra afm would be nice but not available right now.

 

Could I use a voltage divider? with a diode to keep from back feeding or is it an issue?

If im understanding it right with 2 resisters, 500 and 68 gives .6 v but exactly how do you wire it. i keep seeing 2 different ways.

side note I happen to have 68 ohm 1/2 w resisters...why I have no idea

 

so I figured out that low ohm resister in a divider equal toast.. so I went with 270k and a 100k pot. with a diode. on the bench it works adjust from .8 to 0, plug it on the truck with the wiper disconnected same result. connect the wiper and no back feed, but it drops past the divider v without a hick up no change?

did i get to carried away on the ohms and am not flowing enough Ma? though i had it and did a nice job for me of organizing the afm to fit it all but now I messed up something.

help guys
Casey

Edit: so I removed my mess from the afm, because I realized that trim pots are a ready made divider.....stupidity abounds, so I'm simplifying the thing to a diode and a trim pot of the 10k variety. now I'll set the pot with the wiper on and I hope bingo. this arrangement lets me set the volts between 3 and 0 after the diode and setting for 1.5v gave me .4 after the wiper was attached. currently my pot is being glued into the housing. so yea I suck at this.