• 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.

Just a simple question?

Status
Not open for further replies.

estarapapax

New Member
Please look at the very first image in the page provided by this link:

http://www.aaroncake.net/Circuits/supply.asp

My problem is very simple. I currently don't have any idea on how I will add a LED in that circuit so that whenever a load is connected (of course Vin must be connected to the outlet), the LED will light up. I doubt if I will just put it in series with the load. Just tell me the nodes to connect and if additional resistors are needed. Or maybe just provide me a link which has a similar circuit but with a LED. Thanks.
 

Willbe

New Member
how I will add a LED in that circuit so that whenever a load is connected, the LED will light up.
Inside of a high-side switch, this is a high-side sensing circuit.

To turn on a transistor, you need about a minimum of 0.7v, b to e. 5A at 0.7v is 0.14Ω and dissipates ~4w. Put this current sensing resistor in series with the reg. IC input line.
This resistor needs to be adjustable; I'd make this resistor out of about 1' of #30 wire wrap wire.

Hook up a PNP transistor with the e terminal upstream of this resistor and b terminal downstream. Put a 1kΩ resistor in series with the base lead.

Run the collector lead through a 40/.02 = 2kΩ resistor through your LED to ground.
The breakdown voltage of this transistor needs to be >40v.

If you need a snap-action turn-on for the LED, or if you need the LED to turn on at very low load currents, this circuit will get more complicated.
 

audioguru

Well-Known Member
Most Helpful Member
The values of the resistors in the project are for the more expensive LM117. They should be a 120 ohm resistor and a 2.5k pot for an LM317.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top