Hello to all on the forums- I am trying to turn on a lantern at night - the lantern pictured comes with a solar panel but my model does not-i would like to use a solar panel to charge it and turn it on at night using the panel as the dark sensor

 

Grab a solar powered garden light LED string and it already does exactly what you want. There are data sheets around for the common control ICs used in them. That may be a good place to start.

 

Grab a solar powered garden light LED string and it already does exactly what you want. There are data sheets around for the common control ICs used in them. That may be a good place to start.

Most of which only need 1 nickel cell, and the inverter oscillator produces enough voltage for any colour LED.

Most use a chip nowadays, and the solar panel input also senses whether to turn the LED on. Earlier discrete component types mostly used a complimentary astable driving the inductor. LDR use were common early on, but variants involving an extra transistor evolved over time.

 

Grab a solar powered garden light LED string and it already does exactly what you want. There are data sheets around for the common control ICs used in them. That may be a good place to start.

I was going to say it's a good place to end also: Just hack a landscape light to turn on the lantern instead of the LED it came with. But then it dawned on me that the LED in the lantern likely uses a LOT more current than a little landscape light. The landscape light may work for the switching, probably you'd want to add a transistor, but it won't be able to drive the LED with its tiny boost circuit.

 

The thing is I already have the lantern - all I want to do is charge it with a small panel a d then switch it on using said panel

 

i would like to use a solar panel to charge it

What type of battery is inside your unit?
SG

 

What type of battery is inside your unit?
SG

I'm not sure it's probably a cheap basic cell phone type

 

I'm not sure it's probably a cheap basic cell phone type

From photos of the unit I see a three cell battery pack. The add says it is a lithium ion. That would be about 11.1 volts. Does your unit have the ac cord charger?
SG

 

Yes I still have the cable - I was thinking of cutting it and connecting the panel that way - the diagram I posted of the circuit may require a different diode to prevent the panel drawing power at night

 

I was thinking of cutting it and connecting the panel that way

Cutting the ac cable?
SG

 

Yes the AC cable as the inlet port has a two pin connection

 

Yes the AC cable

You can't do that. That input requires 120 vac.
SG

 

Yes but it converts it to DC - how Many things do you know what run off just ac

 

Yes but it converts it to DC

OK so your plan is to cut the plug off the ac cord and connect the solar panels to this cord?
SG

 

Yes that's my plan Ive seen things like flourescent bulbs and tubes run off joule thiefs- I understand that it's different to solar - could I just take out the AC gear and hook up the DC output as long as I add resistors

 

could I just take out the AC gear and hook up the DC output as long as I add resistors

That is what you would need to do but without a schematic it's difficult to advise.
SG

 

As a rule, using a connector which normally has mains voltages on it for love voltage DC is bad. That connector isn't unusual, and if someone connects an intact line cord, electric shock and/or fire is a possibility.

There is a good chance that latter is unsafe even as it is. Many of that type have a capacitive dropper supply and they are not isolated form the mains. All very scary.

 

As a rule, using a connector which normally has mains voltages on it for love voltage DC is bad. That connector isn't unusual, and if someone connects an intact line cord, electric shock and/or fire is a possibility.

There is a good chance that latter is unsafe even as it is. Many of that type have a capacitive dropper supply and they are not isolated form the mains. All very scary.

Non-isolated droppers violate the terms of this forum.

 

Let's not get excited, the AC is left behind and might have a SMPS inside. As almost always we need more information on what is on the inside.

 

Ok here are more pics