Hello everyone, this is my first post here.

I'm trying to repurpose Dollar Tree solar lights to run other things than just the LED light, this is for a little hobbycraft.

The little PCB has a YX8018C chip on it. (some pictures included below, sorry if a bit blurry). It has a 300 mah 1.2V NiCad rechargeable battery to power it.

I'm very novice with electronics. I know how to solder and I have a multimeter, but I don't have much experience with capacitors, diodes, diffusers, etc.

I tried just removing the LED light and wiring a very small electric motor to it (I used a tiny tail rotor motor off of a cheap toy RC helicopter). The motor ran fine, but it would run regardless of whether here was light on the solar cell or not.

I want to see if I can do this very inexpensively. I'm just needing some advice on what exactly I should do. I want the DC motor to turn on when the LED would normally turn on and off.

Thank you for your time.

 

Welcome to AAC.

It's not likely you'll find much use for solar lights other than solar lights. As for the motor running all the time - I don't have a clue. Perhaps it's pulling the PVP (Photo Voltaic Panel) (solar battery) down low enough that the circuit thinks it's dark and time to turn the light on.

 

Welcome to AAC.

It's not likely you'll find much use for solar lights other than solar lights. As for the motor running all the time - I don't have a clue. Perhaps it's pulling the PVP (Photo Voltaic Panel) (solar battery) down low enough that the circuit thinks it's dark and time to turn the light on.

I posted this on reddit and only got 2 replies, one guy said I could remove the inductor and in its place install the DC motor in parallel with a small capacitor. He said to keep the LED in the system because it sorta works like a diode??? But I don't know what size capacitor to try in this instance, if that configuration will even work.

I'm hoping I'm not the only one to think of repurposing a cheap solar light circuit to do something similar to this. I found some guys who looked at the YX8018 schematic and proposed things, but I need more help with my lack of electrical knowledge.

 

Post a link of the schematic you have. I don't see any inductors on the board.

 

The inductor is on the top in the bottom photo in post #1, marked L1.

 

I found some guys who looked at the YX8018 schematic and proposed things, but I need more help with my lack of electrical knowledge.

The way you had the motor connected in place of the LED is correct.
The solar cell charges the battery during the day and also is the light sensor to activate the LED when it gets dark outside.

 

The inductor is on the top in the bottom photo in post #1, marked L1.

Thought that was a resistor. L1 kind of didn't stand out to me at first.

 

Of course the motor will run, if the solar cell is not supplying voltage. The solar cell voltage is used to switch off the LED when it is illuminated during the daytime.
In addition, guessing from the appearance of the remains of the LED leads, it is likely that the LED connections were short circuited to each other during the removal process. THAT may have damaged the series switch .
Try shining a bright light on the solar cell connected to the PCB in place of the LED and see if that switches the motor off.

 

Did you try it outdoors in direct sun? Indoor light might not be bright enough to turn it off.

 

Post a link of the schematic you have. I don't see any inductors on the board.

Here's a link to the datasheet for the YX8018 control chip
https://asset.conrad.com/media10/ad...ru-components-tc-9744120-linearny-io-bulk.pdf

 

Of course the motor will run, if the solar cell is not supplying voltage. The solar cell voltage is used to switch off the LED when it is illuminated during the daytime.
In addition, guessing from the appearance of the remains of the LED leads, it is likely that the LED connections were short circuited to each other during the removal process. THAT may have damaged the series switch .
Try shining a bright light on the solar cell connected to the PCB in place of the LED and see if that switches the motor off.

When I removed the LED and wired the DC motor to the same spot, the motor would run, but it would not stop running when light was on the solar cell (and I did test with direct sunlight as well). And I tested this on multiple solar lights that I bought from the Dollar Tree for $1.25 each, it gave the same result for each one.

The explanation from a reddit user ferrybig is below (I left all his spelling unchanged, I think he's from europe):


The circuity is really simple, the YX8018C looks if the solar panel is producing voltage, and if it isn't it keeps pulling a pin to ground, followed by it floating many times a second, so the inductor on the board acts as a boost converter. I then depends on the leds having a higher forward voltage than the battery voltage, so they stay off.

To repurpose this chip for a DC motor, remove the inductor, then add the DC motor in the place where the inductor was, with a small capacitor in parralel. Its switching speed of around 512khz will be filtered by the capacitor

EDIT: Previeus instructions said to remove the led, it shouldn't be removed as it acts as a inductive kick back blocking diode. You can use a normal diode or another led from LX to VCC as an alternative

I tried to ask him a follow-up question, but he never responded back.

 

Did you try it outdoors in direct sun? Indoor light might not be bright enough to turn it off.

Yes. I used sunlight and tested on more than one cannibalized Dollar Tree solar lights.

 

MisterBill2 (post #8) has sparked an idea; maybe a snubber diode across the motor MIGHT help. After all, the motor commutator is going to be causing some Back EMF (BEMF) which might be the reason why the motor runs on and on. Here, let me show you:

In the drawing below there's the LED on the solar light unit. (which you removed - and that's probably OK) I didn't bother to draw out the whole thing, that's not necessary to my point, that a snubber diode might be the remedy. If not - no big loss. The diode goes directly across the motor pointing the cathode toward the positive lead. This way it won't short out across the motor but when the motor commutator fires off a BEMF the diode may shunt it. The whole thing might even run better. I don't know, I don't have a solar light to play with. But a diode is just a simple test. If it doesn't work, and don't hold out high hopes for it to, it doesn't really cost you much at all.

 

MisterBill2 (post #8) has sparked an idea; maybe a snubber diode across the motor MIGHT help. After all, the motor commutator is going to be causing some Back EMF (BEMF) which might be the reason why the motor runs on and on. Here, let me show you:

In the drawing below there's the LED on the solar light unit. (which you removed - and that's probably OK) I didn't bother to draw out the whole thing, that's not necessary to my point, that a snubber diode might be the remedy. If not - no big loss. The diode goes directly across the motor pointing the cathode toward the positive lead. This way it won't short out across the motor but when the motor commutator fires off a BEMF the diode may shunt it. The whole thing might even run better. I don't know, I don't have a solar light to play with. But a diode is just a simple test. If it doesn't work, and don't hold out high hopes for it to, it doesn't really cost you much at all.

View attachment 336033

Thank you for drawing that out for me. What diode size should I try? Is there a range of sizes I should get to try out? I was looking around on Amazon, and I see they sell diodes in assortment kits with certain ranges.

 

Not the expert here, perhaps a fast diode like a signal diode. If not - a 1n4004 should be good enough.

Since nobody has raised a counterpoint it may be worth investigating.

 

Probably the voltage rating will not matter, because of the very low voltage levels. The current rating would probably disqualify some signal diodes, so switching speed and the related charge storage will matter most. That points toward small power diodes.

 

Probably the voltage rating will not matter, because of the very low voltage levels. The current rating would probably disqualify some signal diodes, so switching speed and the related charge storage will matter most. That points toward small power diodes.

Where do you guys buy diodes from? Amazon? Or do you have a better resource?

 

Where do you guys buy diodes from? Amazon? Or do you have a better resource?

I used to buy them from NEWARK and Pioneer electronics. Then I got a bunch of stuff from a company that was going out of business. I have not used up that stock yet.

 

Where do you guys buy diodes from? Amazon? Or do you have a better resource?

If I'm building some cheap toy - Amazon. If I want quality parts I go to Digikey.com

 

If I'm building some cheap toy - Amazon. If I want quality parts I go to Digikey.com

The nice thing about Digikey is they deliver to me, (Canada) next-day air for CAN$8.00 , on my door step next AM.
All customs free, and free postage if order over $100.