Electronically activated switch

[troy310589]

Hi, i got a simple circuit design that consists of a battery, resistor, led, capacitor and a switch. what i want to do is replace the manual switch with something automatic.. in a way.

**broken link removed**
NOTE: Dont bother if the symbols are wrong, i was trying to do it from memory.

i want the switch to be activated by a 1-12v current (any number from 1 to 12, as this voltage will change a fair bit during operation.) i want some sort of switch that can detect volts in this range and pass current through it, and i dont want the 1-12 v coming into the swith to affect the current of the switch.
i hope this is clear, let me know if it isn't

 

[Russlk]

This is one way to do it:

 

[troy310589]

hmm, ok, i cant make any sense of that, but it looks impressive where does the LED go?

 

[ZIGGY_DAN]

Iv'e included a diagram that will turn on the LED when the light levels increase, you could swap R1 and R2 and then the LED will illuminate when the light level falls, or you could replace the LDR(R2) with a thermistor or even a moisture sensor.

hope this helps

 

[troy310589]

Iv'e included a diagram that will turn on the LED when the light levels increase, you could swap R1 and R2 and then the LED will illuminate when the light level falls, or you could replace the LDR(R2) with a thermistor or even a moisture sensor.

hope this helps

yeh, that kinda helps, if i replaced the ldr with my 1-12v input, would that still work? and whats the physical size of these components? i am restricted in space

 

[AllVol]

whats the physical size of these components? i am restricted in space

Here is another variation on the same theme, using a simple 2N222 transistor. On a breadboard, all components will fit inside the diameter of a quarter (American money, by the grace of God).

AllVol

 

[ZIGGY_DAN]

yeh, that kinda helps, if i replaced the ldr with my 1-12v input, would that still work? and whats the physical size of these components? i am restricted in space

yes, i believe that this would work also, my circuit simulation software indicates that it would work fine, as far as size goes it could be made to fit into a small box of matches with room to spare, the only size issue would be the batteries, you could use coin cells, the kind found in watches.

the voltage at whitch the LED will illuminate is set by VR1, a 100K potentiometer.

hope this helps

 

[troy310589]

What software program do you use?

 

[ZIGGY_DAN]

I use livewire from new wave concepts, it's pretty good, although i would be happier if there were more components in the database. cost me about £15 at maplin electronics(it was on special offer)

here is a link to new wave concepts:
https://www.new-wave-concepts.com/products.html

and maplin electronics:
**broken link removed**

price has gone up to £34.99

hope this helps