Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Switch design!!

Status
Not open for further replies.

shamyluppal

New Member
i want to design a switch with the control signal being a 5-volt or a 0-volt and the input signal ranging between 0 and 15 volts. I tried using a transistor as a switch, but that gives 0 volts if the control signal is 0, when actually i want it to be a high impedence state. And if the control signal is 5-volts, the output shud be the same as the input.
Can someone plz help me??
 
Re: State buffers!!

shamyluppal said:
i want to design a state buffer with the control signal being a 5-volt or a 0-volt and the input signal ranging between 0 and 15 volts. I tried using a transistor as a switch, but that gives 0 volts if the control signal is 0, when actually i want it to be a high impedence state. And if the control signal is 5-volts, the output shud be the same as the input.
Can someone plz help me??
I'm not sure why you call that a "state buffer", but you can do this with one section of a CD4053. Tie all unused pins to GND except the unused "contact" on the switch that you choose to use.
 
Re: State buffers!!

Ron H said:
, but you can do this with one section of a CD4053. Tie all unused pins to GND except the unused "contact" on the switch that you choose to use.

In order to "pass" 0-15VDC signal via the multiplexer 4053, 4053 needs to be powered with 15V or more. The range for control voltage must be at least 0-8V which the original poster might not have.

Another alternative is to use a bilaterial switch like cd4066 and use NPN transistor together with one of the switch for control level translation.
 
Re: State buffers!!

eblc1388 said:
Ron H said:
, but you can do this with one section of a CD4053. Tie all unused pins to GND except the unused "contact" on the switch that you choose to use.

In order to "pass" 0-15VDC signal via the multiplexer 4053, 4053 needs to be powered with 15V or more. The range for control voltage must be at least 0-8V which the original poster might not have.
You're right, L.Chung. I misinterpreted the datasheet. :oops:

Another alternative is to use a bilaterial switch like cd4066 and use NPN transistor together with one of the switch for control level translation.
I was originally going to suggest this. I should have listened to my instincts. :roll:

Ron
 
Russlk said:
If high speed switching is not needed, the best way is to use a solid state relay, like Omron G3VM.

Agree. Before yours suggestion I always thought of solid state relays as high voltage (>10V) devices.

Full isolation, no power supply needed and less than $2 each, requires nothing but one additional resistor for the application to work, it is an amusing solution.
 
shamyluppal said:
i want to design a switch with the control signal being a 5-volt or a 0-volt and the input signal ranging between 0 and 15 volts. I tried using a transistor as a switch, but that gives 0 volts if the control signal is 0, when actually i want it to be a high impedence state. And if the control signal is 5-volts, the output shud be the same as the input.
OK, so the control will be either 0V (in which case the switch is off, and the output should be... what, precisely? When you say, "high impedance state," what exactly do you have in mind to send the output to? Or do you mean that the input should be in a high impedance state?

Or the control will be 5V, in which case whatever is at the input of the switch is at the output. Now, when you say "whatever," what kind of signal exactly is it that you want to switch? Is it digital, or analog? How precise does the copy at the output need to be? With a little more detail, I'm sure you'll get a much better answer.
 
Wire a transistor in common collector mode. Tie collector to +ve, base to your source (0 or 5V), and your emitter to output.

and you might want to add a resistor between emitter and output to prevent the transistor from burning out.

and just how high does the impedance have to be?
 
when the controlling signal is 5 volts, the switch should pass a range of 10-20 volts dc (almost whole of it). When the control is 0, it should give high impedence (open circuit equivalent) at the output.
 
shamyluppal said:
when the controlling signal is 5 volts, the switch should pass a range of 10-20 volts dc (almost whole of it). When the control is 0, it should give high impedence (open circuit equivalent) at the output.
This is not what you stated originally (0-15V). What is the entire range of input? Is it 0-15, 0-20, 10-20, ...?
 
shamyluppal said:
when the controlling signal is 5 volts, the switch should pass a range of 10-20 volts dc (almost whole of it). When the control is 0, it should give high impedence (open circuit equivalent) at the output.

Try telling us EXACTLY what you want to do, so far you are only posting vague ideas - so far you've had eight replies, not of which are probably helpful?. If you don't explain what you are trying to do, how can we offer suggestions?.
 
Yes, it would be helpful. For instance, a classical Class A amplifier presents the impedance looking back into the collector output resistor (more or less) when it is off. It duplicates the input signal, with varying degrees of accuracy, but out-of-phase. So does out-of-phase matter to you? Is this (for instance) an AC or a DC waveform? If it's AC, you don't care if it inverts, most likely- if it's DC, however, it is totally useless for this purpose.

Both of these, of course, assume that the signal of interest is an analog signal. But if the signal is digital, you don't care about the waveform- just when its on and when its off.

Please tell us more about your application.
 
Sorry for the mistake... typed a '1' by mistake....now anyone just tell me what is the internal circuitry of the tristate buffer...how does it work?....i'll try to think sumthing on my own!!!!
 
shamyluppal said:
Sorry for the mistake... typed a '1' by mistake....now anyone just tell me what is the internal circuitry of the tristate buffer...how does it work?....i'll try to think sumthing on my own!!!!
I am not going to comment further until you answer Nigel's question.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top