simple transistor circuit

is there a simple transistor(or any) circuit that could be used to detect a specific(range) voltage, say if a input was 2-4volts the output would show a logic 1,, but with 0-2or4-6volts would be logic 0?

If you need the detection to be precise on 2 and 4V, then use two comparators and a logic gate.

However, if you don't mind to spend some time to adjusting a transistors emitter resistor - then there should be easy to make one.
Have in mind that the "easy" variant will not be suitable for further voltage window adjustments.

Working from Grossel's suggestion think about using a LM393 configured as a "window comparator". Read through this link to the window comparator section. That should get you going. Also note the use of hysteresis in comparator circuits.

Ron

well it is ok if the detector is fixed, but i would want more of a switching system where it detects from 2 to 2.2v(within that range), then the next similar circuit will switch from 2.2 to 2.4, the more precision the better, i would make 25 or so of these


im hoping to keep it to 2 transistors, few resistors, maybe a capacitor, i want it to switch on right away then delay a few ms(tops maybe) after the signal to offstate, \

that window circuit is definitely what im looking for, but if I kept that window narrow enough would I be able to do that with just one amp?

Initially you stated:

simple transistor circuit

is there a simple transistor(or any) circuit that could be used to detect a specific(range) voltage, say if a input was 2-4volts the output would show a logic 1,, but with 0-2or4-6volts would be logic 0?

Click to expand...

That implies a single window between 2 to 4 volts. I suggested a chip (LM393) consisting of two comparators to create a window comparator. This is not going to happen with a few transistors. Now you come up with this:

well it is ok if the detector is fixed, but i would want more of a switching system where it detects from 2 to 2.2v(within that range), then the next similar circuit will switch from 2.2 to 2.4, the more precision the better, i would make 25 or so of these
im hoping to keep it to 2 transistors, few resistors, maybe a capacitor, i want it to switch on right away then delay a few ms(tops maybe) after the signal to offstate, \

that window circuit is definitely what im looking for, but if I kept that window narrow enough would I be able to do that with just one amp?

Click to expand...

No, each window comparator requires two comparators to set an upper and lower limit. Yes, you can have tight tolerances on the limits and yes, the limits can be adjustable by using post to set the reference voltages to the comparators. What exactly, in detail, are you trying to do. I suggest you read the link I gave you in detail and get real friendly with comparators. Look at the data sheets for the three comparator ICs covered in the link.

Ron

The LM3914 Dot/Bar Display Driver maybe a good option, 10 outputs, can drive TTL or cmos logic levels and can be cascaded for more outputs.
and requires few external components.

kg8gp said:

The LM3914 Dot/Bar Display Driver maybe a good option, 10 outputs, can drive TTL or cmos logic levels and can be cascaded for more outputs.
and requires few external components.

Click to expand...

I thought about suggesting the LM3914 but figured I would wait and see exactly what the OP has in mind. The LM3914 is linear and uses a single Vref so I am not sure it will work for whatever the OP has in mind which seems to be growing.

Ron

you know me too well!
my intent IS to run an led array, but my challenge is to do it on 3 wires, the WINDOW is exactly what im looking for, and is simple enough, opamps still scare me a bit, i mean im fine with them when they only have vcc, gnd, out, +, -, but they get even more confusing when they start poking wires out the bottom and top of the triangle, esically when there are 3 out the top....

initally i planned to use a pnp transisor and and npn transistor in series with the led, and set the base pins to work as an AND circuit
where one base would switch off for the one side of the window and other transistor base to switch for the other side of the window, in the simulator i got each edge to work independently but then couldnt get it to work when i put them together and i dont know why>?


planB was to use a rf switching signal and band filters to trigger the switches, but then i thought that maybe an analog voltage may be easier,

Drawing added (I feel nice today)

I've a solution that should work.

It takes two PNP's and three NPN's to make it. And of course, you have to adjust the pot's to make it trig on the correct voltage.