Voltage detector circuit 12v-40v

[starboard008]

Hi,

I am designing a circuit which need to be triggered by a random voltage and polarity.

the voltage can be between 12v to 40v...

any ideas what component to use??

 

[ronv]

Needs More data.

0 v to 12v - 40 volts or 12 to 40 volt input?
What output?

 

[starboard008]

this is going to be a trigger circuit. I need it compatible with other systems which give both 12v and some of them 40v. the polarity may vary too

 

[ronv]

That wasn't much help.

 

[starboard008]

I want to do a circuit that can be switched on from an existing system. There are different types of systems.. there are sytems with 12v output, 30v output and even 40v output. THe circuit that i need to do must be compatible with all systems, thats why i need it to work at different voltage inputs.

The circuit that i need to build is like a switch, when it receives a signal of 12v, 30 or 40 it switches on. hope i was a bit more clear now

 

[4pyros]

You can a SSR

 

[starboard008]

Thanks.. is there any one in particular so i can check the datasheet?

 

[4pyros]

What you you going to switch? AC,DC and at what current,do you need dry contacts?

 

[crutschow]

You mention polarity. Must it detect -12V, -30V, -40V, as well as +12V, +30V, +40?

 

[starboard008]

i just need a trigger for the microcontroller. so the circuit will trigger the input of the microcontroller when a voltage of 12v, 30v or 40v is present.
Can a solid state relay work with different voltages like what i need (12, 30, 40v)?

 

[starboard008]

Anyone know whit a solid state relay with 12v to 40v dc input?

 

[MikeMl]

A few more questions about your requirement?

How precise do the trip levels need to be? (e.g. is 38 to 42V ok for the 40V trip point?)

How much current can the voltage detector draw from the voltage being sensed?

Can the microprocessor ground pin be tied to the ground for the voltages being sensed? (If so, why not just use a uP with an A/D converter with a suitable resistive divider?)

 

[starboard008]

no need to be precise... the user can connect and input of 12v to 40v and the circuit must still switch on... I cannot use an a/d as the polarity can be changed.. (the user can swap the wires of + and -)

 

[MikeMl]

Do you need to have separate detectors for -40V and +40V? [In other words, is -40V different than +40V? Or is is it OK if a single Detector Output is true when (Vin > 40V) OR (Vin < -40V)? ]

You never answered the question about the common ground between the uC and the circuit being monitored or about how much current the detector can draw?

 

[4pyros]

Can a solid state relay work with different voltages like what i need (12, 30, 40v)?

Have you even looked? Is your google finger broken?
I will give you a hint, I/O

 

[MikeMl]

Here is my hack at it: Use the A/D in the uC to read the voltage at Vout. Input is isolated from the uC's ground pin. You may have to adjust R1 to make V(out) to be ~4V when V(in)=40V.

 

[4pyros]

Mike; That may work with an A/D input but not with an I/O pin. IF I was using an I/O pin I would use a constant current regulater feeding an optoisolater. Andy

 

[MikeMl]

The 4n35's output current is more or less proportional to (vin-4). If he uses an A/D, he can roughly measure a voltage range between ~±10V and ±40V. If he wants just a single ±trip point, then run V(out) into a comparator (either external or internal to the uC).

 

[OlPhart]

I'd use a pair of opto couplers: 1 for each polarity and wire OR the outputs. Feed the inputs thru a blocking diode then thru current limiting resistors to a ~10V zener then another CL resistor to the opto. Size the CLs for reliable op at lowest input and the zener to have enough current headroom to handle highest from there. <<<)))

 

[MikeMl]

I'd use a pair of opto couplers: 1 for each polarity and wire OR the outputs. Feed the inputs thru a blocking diode then thru current limiting resistors to a ~10V zener then another CL resistor to the opto. Size the CLs for reliable op at lowest input and the zener to have enough current headroom to handle highest from there. <<<)))

Even simpler: