Electronics > Projects, Designs, and Technical Stuff

New Component - Current dependent resistor - Need your feedback on the idea

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Harshadb13:
Dear EEVblog members,
Greetings!

I have developed a component of my own and I am calling it as current dependent resistor. I have mentioned below, the construction, the testing and the applications of such a device and I need your comment on the nobility of the idea, and if the idea is really worth something, I want some help on how do I publish it properly. I really couldn't think of any better place to get comments on this idea

Thanks a lot in advance for taking your time to read and comment!

Construction:    (LDR CONSTRUCTION.pdf attachment and LDR REAL IMAGE.jpg attachment)
At its core, it is an LED light (blue in this case) pointing straight at a generic LDR (Light dependent resistor) which I purchased from Ebay. The setup is then enclosed inside a 3D printed case and coated in multiple layers of black spray paint to prevent environmental light from affecting the LDR.

 LDR CONSTRUCTION.pdf (410.57 kB - downloaded 16 times.)    (LDR REAL IMAGE.jpg attachment)



The construction is somewhat similar to a standard opto coupler and the biggest difference being instead of behaving as a transistor at the output is behaves as a resistor.

Testing:

Test circuit image:
    (VOLTAGE LABLES.png attachment)

The voltage labels are as follows:
V1: The main supply voltage for LDR side of the CDR(Current dependent resistor)
V2: The shunt to measure the current flowing through LDR
V3: The voltage coming from the function generator (my Keysight DSO in this case, set to generate a ramp function )
V4: The shunt to measure current flowing through the LED

I have measured the change in voltage of the LDR with respect to in current flowing through the LED.

The resistance of the LDR at any instant would be given by:
(V1-V2)/(V2/R9)/(V2/R9)

However, since R9 is constant, I have eliminated it to get a relative graph. Similarly, to plot the Graph against the current passing through the LED, since R10 is a constant, I have simply plotted the graph with respect to V4.

Thus, the proportionate resistance of the LDR would be given by: (V1-V2)/V2 and the proportionate current through the LED would be given by V4

I have plotted the plot below. I have also attached a graph plotting the inverse of Resistance of LDR vs the current through the LED (shown by plot 1). The plot 1 is almost a straight line which clarifies the relation that the resistance of LDR is inversely proportional to the current passing through the LED.

The Resistance vs Current is shown in plot 2 and 3. (Plot 3 is just zoomed in version of Plot 2) The plot is clearly a function of the nature (y=1/x).

Plots are attached below:
 Current Dependent resistor - DSO Data.xlsx (800.85 kB - downloaded 14 times.)       (Graphs.png attachment)

I have also attached the excel sheet containing the data for the same. Refer sheet two for graphs
[ Specified attachment is not available ]        (DSO Data.xlsx attachment)


Few of the applications that I can think of is using this at he feedback stage of a buck boost converter by which I can control  the output of a converter with a micro controller (ofc with some RC filters to convert the PWM to pure analog valve) and using the circuit to multiply two analog voltages with op amps (I have made and tried the circuit and it works, would make a separate post about that later)


Please let me know your thoughts on the idea and the device. If you think any other parameter might be useful, Please let me know and I will upload it.

Looking forward for your valuable comments and suggestions.

Thank you!

Warm regards,
Harshad Byadgi

Ian.M:
Congratulations on reinventing the Vactrol!

langwadt:
https://www.onsemi.com/pdf/datasheet/h11f3m-d.pdf

wraper:
Such parts are made both off the shelf by component manufacturers or by combining off the shelf LED and LDR. https://sound-au.com/project200.htm There is nothing novel about this, you reinvented the wheel.

Harshadb13:
Hmm... I knew some component would exist that did this job. :-DD :P

The only reason I thought such component does not exist is because great scott made a video on digital potentiometers.

Anyhoo, Thanks for your time and informing me of the components

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