# Unmarked component identification

Discussion in 'General Electronics Chat' started by Fast Eddy, Apr 26, 2010.

1. ### Fast Eddy Thread Starter New Member

Jul 31, 2009
3
0
The attached photo shows a component with no markings, the PCB names it as L1.

I think it may be an inductor ?

Any help accepted

thanks

• ###### L1 Inductor.jpg
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Apr 5, 2008
15,799
2,386
Hello,

There is L1 marked on the PCB.
It is probably an inductor.
It is a coil on an core wrapped with the plasic shrink cover.

Bertus

Fast Eddy likes this.
3. ### kkazem Active Member

Jul 23, 2009
160
27
HI,
As far as this choke (inductor) is concerned, if you want to specify it for the purpose of buying or making additional ones, you should remove L1 and measure the DC resistance and the inductance. It isn't too hard to do. Take a fairly regulated voltage, say 10VDC and apply it to the inductor thru a small current-sense resistor (0.1 ohm). You need a scope for this. Once the 10V is applied, you monitor the current with the scope. The connection of the 10V to the L/R ckt must be fairly quick. It may be possible to do it with a push-on switch, but the best way would be with a square-wave generator. the exact voltage isn't important. What is important is the measurement of the time it takes to get from one current level to another current level. A storage scope (digital) would be best. Then, you can compute the inductance by the formula: L = (E * T)/(I2-I1), where L is in Henrys, E is in volts (volts applied), T is the time over which the current change was observed, I2 is the final current, and I1 is the initial current, which does not need to start at zero.

There is another way if you have a sine-wave generator and a film cap of about 0.1uF to 10uF, with a capacitance tolerance of preferably not more than 10%. Make an LRC series circuit with a small value of R, lets say 1 ohm or so. Make the resistor the bottom-most element of the LRC series ckt and apply the sine generator across the circuit with the generator's ground to the bottom of the resistor and use a scope (no need for storage scope here) between the ground and the top side of the resistor. Now, start at a low frequency and sweep the frequency up until the sine voltage across the resistor is at a maximum. In other words, it should peak at some frequency, then go back down as the frequency is further increased. Note this frequency, Fo. Compute L=1/[(2*pi*Fo)^2]/C, where Fo is the resonant frequency and C is the cap value. If you don't have a scope, you can even use a DMM with an AC volts scale to find the frequency where the voltage peaks.

Once you have the DCR and the L value, you should be able to find an off-the-shelf inductor with similar characteristics from DigiKey or Newark Electronics, or Mouser Electronics, etc.

Good luck.
Regards,
Kamran Kazem

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4. ### Fast Eddy Thread Starter New Member

Jul 31, 2009
3
0
KKAZEM & Bertus

Kkazem, You have just gone way over my head for the moment, I am a novice but keen.

I am trying to fix my torch, it only cost £10, (UK)
But in the process I have decided to learn from it and then hopefully move further into electronics etc etc.

So I decided to identify all the parts on the board and then work out what they all should be doing and hopefully find the fault.

Does that makes sense or do you know a better way ?

Fast Eddy

Apr 5, 2008
15,799
2,386
Hello Fast Eddy,

If you want to know more about the components take a look at the links of these pages of the EDYCYPEDIA:
http://www.educypedia.be/electronics/componentspas.htm

Passive semiconductors technology: Batteries Diodes Photovoltaic systems Switches Buzzers Diode types Quartz crystals Thermoelectric Capacitors General overview Relays Transformers Capacitor types Heat Sinks Resistors Transformers-RF Coils Photo diode Resistors-Nonlinear Transformer types

If you have more questions about "unknown" components, we are happy to try to answer them.

Greetings,
Bertus