# Solar Mailbox Light - Help Needed!

#### caitlinswim

Joined Jul 16, 2013
1
Hi there, I'm just starting out in a new engineering firm and my first task is to take a $2 solar light and put a switch in it so that when a mailbox is opened it will light up in the back. It needs to work under these conditions: Mailbox closed while dark --> LED off, battery not discharging Mailbox closed while light --> LED off, battery charging Mailbox open while dark --> connect circuit normally Mailbox open while light --> connect circuit normally I guess I don't know where the switch needs to go in the circuit, or what kind of switch it needs to be. I don't know how to make sure the battery does not discharge during the night. Also, there is a part in this circuit with the product name YX8018 but no matter how hard I look, I cannot figure out what this part is. What am I doing wrong? Any help and knowledge that can be given would be greatly appreciated. Picture of current circuit is attached. #### Bernard Joined Aug 7, 2008 5,335 Looks like adding a NO SW in LED path should work; all other functions are already taken care of? #### ErnieM Joined Apr 24, 2011 8,009 Do you really care if the LED comes on in the daytime? All you would need is a solar cell, a NiCad, a nice schottky diode, a micro switch, resistor, and your LED. The XY8018 you found is one of the now ubiquitous application specific used in garden lights. I've been seeing similar devices since 2011. The are an improvement over the discrete transistor designs as they use way fewer parts, especially just one (not two) inductor and they don't need the CDS photo resistor. They turn on the LED when they detect the solar cell is in the dark. I see no way into tricking it into working your way. #### wayneh Joined Sep 9, 2010 16,128 ...my first task is to take a$2 solar light and put a switch in it so that when a mailbox is opened it will light up in the back.
Is this just a test, or a product development project?

Anyway, are you constrained to using a particular solar light? they have different circuits and one with a separate CdS cell would be easier to hack. You could just cover the CdS cell so it's always on and instead leave control to a switch triggered by opening the mailbox.

#### ErnieM

Joined Apr 24, 2011
8,009
Anyway, are you constrained to using a particular solar light? they have different circuits and one with a separate CdS cell would be easier to hack. You could just cover the CdS cell so it's always on and instead leave control to a switch triggered by opening the mailbox.
If you can still find a light with the CDS cell you'd just replace it with a door switch: closed for door closed/off and open for door open/on.

#### Bernard

Joined Aug 7, 2008
5,335
Make SW 2P ST NO, one section to close LED ckt, the other to short the solar panel to make it think that it is dark when box is open. Add a zener diode in parall with LED & NO SW to protect IC, around 5V, higher would be better but IC specs are unknown.

#### ErnieM

Joined Apr 24, 2011
8,009
Make SW 2P ST NO, one section to close LED ckt, the other to short the solar panel to make it think that it is dark when box is open. Add a zener diode in parall with LED & NO SW to protect IC, around 5V, higher would be better but IC specs are unknown.
Ummm... I can't translate most of that but...

If you OPEN (don't short) the solar panel then you trick the IC into lighting the LED.

However, there is a condition that occurs every day where the entire Earth impeded the passage of light from the sun. It is called "nighttime" and during these events the LED will be on until it drains the battery.

Don't mess with things in parallel with the LED: the circuit works as a boost switcher to drive the 3-4 V LED off a <1.5V battery.

#### Bernard

Joined Aug 7, 2008
5,335
" believe this is a dead post, good for our own inrertainment. What does IC see from SP, solar panel, at night = 0 V, shorted = 0 V. SP open, IC sees floating lead, does it oscillate, think it's light or dark? With L no load what is V, 30 or more Vs ?