Relay or IC to turn on a circut with around 2,5-3volt

[rollaboy]

Hello, i am new here on the forum. I play with different electronic as a hobby. I know how to solder but im a beginner when it comes to different components etc.

So i would like to hear if you can help me here.

I have a circut that needs to be switched on. I went to my local electronic dealer. He dont have a small relay or circut that work as a switch.

Is it possible to buy a small relay or would it just eat all the voltage just to work?

maybe what i need is something like a IC or something. Its only needed as an on/off switch for my circut and using as little power as possible.

I hope you guys can help me as i'm totally green in the IC circut world!

Thank you very much.

 

[MikeMl]

What battery (voltage) are you planning to power the relay? I'm assuming that you want to pull-in the relay when the input signal is greater than 2.5V, but that the 2.5V signal is not actually supplying the power to pull the relay.

What do you want to switch with the relay?

 

[Jon Wilder]

You would typically have a regulated supply that powers the circuit that you're switching on/off with the relay, then power the coil from the unregulated side of the power supply. The key here is to make it so that when the relay is engaged it only pulls the unregulated side of the supply down to the relay voltage. The circuit being powered from the regulated side shouldn't see the regulated supply voltage change when the relay engages/disengages since the regulator buffers that circuit from the unregulated side of the supply.

 

[Jaguarjoe]

I have no clue what you're doing, but here's a cheap 3 volt relay that may help you.

**broken link removed**

 

[rollaboy]

Thank you for your quick reply.

We have tried with a small relay but it drains all the power. So we cannot use a relay.

But isnt it possible to use some kind of IC switch theres using almost no power?

Actually it should turn on the other circut when theres any voltage to the IC. It doesnt have to be 2,5 or 3 volt. It can be lower as well.

So basically we just need a switch to turn on a circut when theres any small voltage to the switch.

 

[KMoffett]

"Actually it should turn on the other circut when theres any voltage to the IC."
Possibly an NPN and a PNP transistor and two resistors, to switch on above 0.6v input. What's the voltage to the"other circuit"?

Ken

 

[Jon Wilder]

Sounds like you have too large of a relay for the application and a power supply that doesn't have enough current to run the relay that you're trying to use. To switch a 2.5-3 volt circuit you don't need such a large relay. An Omron G5V-2-H1-DC5 5 volt high sensitivity relay can switch a low voltage circuit like that and the coil only draws 30mA.

 

[rollaboy]

We dont have much amps to drive a relay so we dont think thats an option.

So we are looking for a simple ic switch that can activate our other circut when it senses any voltage and cut off automatically when theres no voltage again.

isnt that possible?

Or do we need all kind of transistors and other stuff? we just need like a relay that almost doesnt use any power. but mechanical relays takes up 30mA or 50mA and thats too much.

Thank you guys.

 

[Jon Wilder]

Not enough amperage to supply 30mA? What power supply are we dealing with? A schematic along with a part number for the transformer would help.

 

[rollaboy]

We are working with a solar cell as a power supply. and when it starts to make energy it should turn on the other circuit.

Sorry but we a newbies and dont know alot about different components. We a not electronic guys, but more auto mechanic guys and work with cars for a hobby. So we know what a relay does and we just need to find a solution like an relay to turn on our circuit.

 

[Mosaic]

Where does the "other circuit" get power from?
The same solar cell?
Sounds like you're talking about 'brown out" control, so that only when the solar cell achieves a voltage the 'other circuit' kicks in?
If your "other circuit" uses a microcontroller then I'd use the brown out config word to achieve the result.

Otherwise a low voltage MOSFET device consumes VERY little power and can switch multiamp loads.
**broken link removed**

 

[Jon Wilder]

So in other words what you're looking to build is a voltage detector. What's the circuit we're powering? Again a schematic would help us out immensely here.

 

[rollaboy]

the other circuit has its own closed seperate power supply and we cannot use any power from this circuit.

Jon, yes you can call it an voltage detector, we just want to find a switch. Isnt it possible with a single component just like a relay does it?

We are total newbies and we have tried to use a ic hef4066bp but we dont know how to get it to work. we cant understand the datasheet and theres 14 pins to choose from.

 

[KMoffett]

Not knowing what the voltages or currents for the "other circuit", this it a version of a power switch that is turned on and off by a low voltage. The values for the resistors and transistors depend on your outher circuit's requirements. More specific details would help.

Ken

 

[Jon Wilder]

the other circuit has its own closed seperate power supply and we cannot use any power from this circuit.

Jon, yes you can call it an voltage detector, we just want to find a switch. Isnt it possible with a single component just like a relay does it?

We are total newbies and we have tried to use a ic hef4066bp but we dont know how to get it to work. we cant understand the datasheet and theres 14 pins to choose from.

Assuming the solar panel and the supply that powers the circuit share a common ground, you could use a simple transistor to do what you're trying to do. Something like this should suffice -

**broken link removed**

 

[rollaboy]

Thank you for the drawings. what paint program do you use to make them?

I tried to make one simple drawing of what i want to do.

i dont want to power my other circuit. Just switch it on. I see it just like when im using a relay to power up the fog lights on a car.

the drawings are almost like another language for me. i hope you can see that this is hard for me to understand. thanks.

 

[Jon Wilder]

Your circuit has to have power to turn on.

You don't need a solar panel for that. A simple photo resistor in line with the power supply feed should suffice. You can use the photoresistor to control the base current of the transistor. Use a photoresistor with a high off resistance -

**broken link removed**

 

[rollaboy]

Ok the other circuit have some other things to it and cannot be touched. so have the first circuit but i cannot explain it in details. i just want to have the first circuit to power on the other one without modifeing any of the circuits. cant there just be a simple switch or relay or something. i dont want to mix up the two circuits. i just need a "bridge" between them. a little switch that turns on the other one when it gets some low voltage and no amps. its that simple. i cant see why i need to do all kind of things. its just a signal to turn the other circuit on with a switch.

can you please help me find a IC or something that i can use as a relay. i dont want to modify all the circuits. because i dont have the knowledge. i'm used to realys and i want to make it as basic as that.

i know it sounds strange in your ears sorry

 

[Jon Wilder]

You're making this more complicated than it needs to be. That's precisely what a transistor will do.

In the circuit above, the photoresistor pulls the base of the transistor down to ground when there is light present. This turns the transistor off and interrupts the circuit's connection to ground, thereby switching the circuit off.

When it goes dark, the photoresistor's resistance goes high and the base is then pulled up to the supply voltage via the base resistor. This allows base current to flow, which then turns the transistor on. The transistor supplies a ground to the circuit it's switching when turned on.

Once it goes light again, the base is pulled down to ground, which turns the transistor off and interrupts the ground to the circuit, switching the circuit off.

The only thing common to the controlling circuit and the controlled circuit is the emitter of the transistor, which is tied to a common reference. This will not affect circuit operation.