# How to activate a circuit when current flows through another given circuit ?

Discussion in 'The Projects Forum' started by 5416339, Aug 26, 2010.

1. ### 5416339 Thread Starter New Member

Aug 25, 2010
8
0
The topic is quite clear ,So i was wondering how we can make such a circuit !

Apr 5, 2008
15,805
2,389
Hello,

How much current is flowing in the "origenating" circuit?

Bertus

5416339 likes this.
3. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Actually the topic isn't clear. Don't assume, it doesn't work.

I assume you want something like the output of a 555 to power a second circuit. Is this even close?

Schematics and examples are your friend.

4. ### 5416339 Thread Starter New Member

Aug 25, 2010
8
0
The originating current is about 5 A

Apr 5, 2008
15,805
2,389
Hello,

Can you post a schematic of the originating circuit?
Is it possible to connect anything to the circuit?

Bertus

6. ### 5416339 Thread Starter New Member

Aug 25, 2010
8
0

Apr 5, 2008
15,805
2,389
Hello,

The mobile bug you show in the link is never drawing 5 A.
With the info provided we can not do anything.

Bertus

8. ### 5416339 Thread Starter New Member

Aug 25, 2010
8
0
Actually my aim is to amplify the PD across the LED terminals currently its just 0.1 V!

9. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
A simple op amp such as the LM358 can amplify a small voltage like that, just set the gain to 10. Since your talking LEDs I am assuming DC voltage.

PD? As in photo diode? If it is how does it apply with this?

10. ### 5416339 Thread Starter New Member

Aug 25, 2010
8
0
Yes it is DC voltage but 10 time higher will not help 50 times is required !!

11. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
So change the value of the resistors. I'm assuming you know how op amps work.

The reason suggested a LM358 is it can go very low to ground.

A LM393 is a comparator, it can do the same thing, but it does not have an analog output. It is strictly on or off. It has an open collector output with an absolute max current rating of 16ma. Less is better, much better.

Apr 5, 2008
15,805
2,389
Hello,

I have some doubts with the circuit provided.
The CA3130 will not work with the RF signal from the phone.
Also the desciption in C3 is very strange, the capacitor wit its leads will never meet the frequency as given.

Bertus

13. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
This is a blast from the past! Just after the Korean War, lots of military components went on the surplus market. A man who styled himself "Madman Muntz" started putting out a line of very cheap TV's using surplus parts.

The fun part was that many of the capacitors were old so-called "body end dot" types in phenolic packages - see the reference for "postage stamp" caps - http://en.wikipedia.org/wiki/Electronic_color_code . The individual capacitances were weenie, but could be made useful by soldering together 5 or 6 of them (possible in the days of point-to-point construction).

Then he got carried away by finding out how many components could be left out and still have the set work. This led to the use of lead dress as a means of adjusting reactances in the set. It also meant they became effectively unrepairable, because disturbing the runs of wiring tended to make the set stop operating.

Found a reference - http://www.freeenterpriseland.com/MUNTZ.html

14. ### marshallf3 Well-Known Member

Jul 26, 2010
2,358
201
Then use different values in the op amp circuit to achieve the desired amount of gain.