These little LED candles are sold in packs of ten or twenty on ebay and designed to be mounted on a tree like fairy lights or Christmas lights. Each one has a AAA cell inside and a common infrared remote controller can be used to turn them on or off, and also adjust intensity and choose a subtle or strong flickering effect.
The information that came with the candles suggests that the standby current is so low that the batteries will last for months in standby and in use the LED current is so low that it should also result in a long battery life. I disagree. I tested the standby current at 0.8mA which is significant for AAA cells.
The construction is very neat. The candle body houses a formed wire connection spring and side contact, while the top that bayonet caps into the body has a small metal cup that makes connection between the PCB and side contact, has a hole to allow the positive battery terminal to make contact with the plated end of the PCB while preventing contact if the battery is put in the wrong way round (it may short the battery though) and also holds the PCB in place, which in turn locks the clear plastic flame section in position. It's a really neat and reliable design.
The PCB has a microcontroller (probably a PIC12 clone/variant), an infrared receiver and a super-neat little 3.3V 3-pin boost chip that uses a small choke and capacitor to create a 3.3V supply from the single AAA cell.
Analysis of the circuitry shows that the infrared receiver is powered from one of the microcontrollers pins, so it can be turned on briefly to see if an infrared signal is being received, then if there's no signal it can turn it back off again, sleep for a moment and then poll the receiver again until it finds a signal.
The LED is driven from a microcontroller pin via a 200 ohm resistor. Any activity on the infrared controller shows that the microcontroller stops dealing with the LED momentarily to concentrate on the infrared activity.
A bit disappointing that the standby current isn't as low as implied in the instructions, but other than that it's a pretty neat design.
The information that came with the candles suggests that the standby current is so low that the batteries will last for months in standby and in use the LED current is so low that it should also result in a long battery life. I disagree. I tested the standby current at 0.8mA which is significant for AAA cells.
The construction is very neat. The candle body houses a formed wire connection spring and side contact, while the top that bayonet caps into the body has a small metal cup that makes connection between the PCB and side contact, has a hole to allow the positive battery terminal to make contact with the plated end of the PCB while preventing contact if the battery is put in the wrong way round (it may short the battery though) and also holds the PCB in place, which in turn locks the clear plastic flame section in position. It's a really neat and reliable design.
The PCB has a microcontroller (probably a PIC12 clone/variant), an infrared receiver and a super-neat little 3.3V 3-pin boost chip that uses a small choke and capacitor to create a 3.3V supply from the single AAA cell.
Analysis of the circuitry shows that the infrared receiver is powered from one of the microcontrollers pins, so it can be turned on briefly to see if an infrared signal is being received, then if there's no signal it can turn it back off again, sleep for a moment and then poll the receiver again until it finds a signal.
The LED is driven from a microcontroller pin via a 200 ohm resistor. Any activity on the infrared controller shows that the microcontroller stops dealing with the LED momentarily to concentrate on the infrared activity.
A bit disappointing that the standby current isn't as low as implied in the instructions, but other than that it's a pretty neat design.
So, just for my own reference, because I lost this damn remote control for my cheapy xmas candles, it's the colorfull ugly setting for a LG TV and program channel down for the LED's to go on and audio mute for the LED's to power off – on an Android app called Rcoid…
You're a baller genius; and I'm not being facetious. Are you still checking comments? I had a quick question for you!
Do you have a link to these candles?
LP2985-33 is a 3.3V regulator made by Texas Instruments. That is your T33 chip in your electronic candles most probably. Maybe I am wrong Clive. Check it out my friend….