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Regulating output of a 5252f?

piercedfreak

Jun 7, 2019
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I am hacking around with a novelty solar garden lamp, and wanted to change the LEDS from white to the colour changing LEDS. I tried just changing the LEDS, but the output from the 5252f seems to oscillate too much for the LEDS to change colours. My thoughts were to just put a small capacitor and diode inline on anode of the LEDS, but I wanted to get a second opinion before I tore it all apart again, and salvaged a capacitor. This system just uses a small 1.5VDC Nimh battery, and drives 2 LEDS. I am a noob, and know nothing about choosing the right capacitor values, so some input there would also be helpful.
 

Harald Kapp

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This will not work.
The 5252f uses a boost converter circuit to increase the batttery voltage to ~3 V for the LEDs see this description. You would have to add a diode between the inductor and the LEDs plus a capacitor parallel to the LEDs. The diode, however, will incur a voltage drop. This may be acceptable if you use a Schottky diode.
The proof is in the doing.
 

piercedfreak

Jun 7, 2019
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This will not work.
The 5252f uses a boost converter circuit to increase the batttery voltage to ~3 V for the LEDs see this description. You would have to add a diode between the inductor and the LEDs plus a capacitor parallel to the LEDs. The diode, however, will incur a voltage drop. This may be acceptable if you use a Schottky diode.
The proof is in the doing.


Ok, thanks. Back to white it is then.
 

Audioguru

Sep 24, 2016
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I converted ALL of my many solar garden lights from a white LED to a colors-changing LED by adding a series 1N5817 Schottky diode in series with the LED and a 0.1uF ceramic capacitor parallel to the LED.

The datasheet for the 5252 IC shows that the inductor sets the current. 150uH gives less brightness and 47uH gives lots of brightness. Of course the battery current is affected by the brightness.

There are colors-changing LEDs that make blinking patterns and others that slowly fade from one color to the next color. Some produce only red, green and blue but others mix the colors to produce many colors.
 

Harald Kapp

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adding a series 1N5817 Schottky diode in series with the LED and a 0.1uF ceramic capacitor parallel to the LED.
Exactly what I proposed only my post incl. schematic got lost :(
Here it is again:
upload_2019-6-14_12-57-2.png
You may need to tweak C1 (e.g. 1 µF) to get the circuit working with your LEDs.
 

Audioguru

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A similar solar garden light IC Prema PR4403 is from Germany. Its datasheet says that its switching frequency is 500kHz. Then the 0.1uF filtering capacitor is fine to smooth the rectified pulses from the output.

You never feed a regulated voltage to an LED since it sets its own voltage and its current sets its brightness. The value of the inductance in the solar IC circuit sets the peak current. The output voltage is high enough to use two LEDs in series and for a colors changing LED that usually has its internal IC operating from 4.5VDC.
 

caps

Jul 29, 2018
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There is a lot of information on LED lamps.
https: slash slash fimopico dot pw slash yx8018.html
[Mod edit: link removed, everybody use that site at their own risk. Thanks @Audioguru ]
 
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Audioguru

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BEWARE! That site has a VIRUS on it. I used CTRL ALT DELETE to get out of it then I changed my User.
 

caps

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