LED Leads & Transistor Leads are rusting away.???

Gary, in your Joule Thief circuit with the added LDR transistor, R2 turns on the transistor and R1 turns it off.
If the battery is 2.7V, R1 is a high value and R2 is very low at 5k ohms then the base current in Q1 is (2.7V - 0.7V)/5k= 0.4mA. Then the datasheet of the transistor says it will saturate very well with an output current as high as 4mA which is much more current that a Joule Thief needs.
Maybe your transistor has its base destroyed if the 100k pot resistance was turned too low or maybe the transistor emitter and collector are wrongly swapped.

The only way I can get a 5K resistor is five 1K in series so I used 4.7K. I tested the once used transistors with a meter they test good. I swapped transistors in bread board circuit to double check they are good. Transistors are all good. I built this circuit Q1 still will not work. I tested voltage to the Joule Thief it = 0. I put a jumper wire across Q1 E to C joule thief comes on.

Gary; Normal batteries start at 1.5V when new but decrease in voltage steadily as they are used, ending up at around 1V before being completely flat and the voltage suddenly dropping rapidly.

At 2.7V for two, 1.35V each, they still have over a third of their capacity available; possibly half or even more.

See discharge curve plots below:

If the power switching transistor does not turn on with a base resistor of 4.7k to 22k then maybe the LDR is not dark enough.
Remove the LDR and replace it with a 200k resistor to see.

What is the Base-Emitter voltage on Q1 under the different operating conditions? Is it enough to turn the transistor on when it should? And is there enough base current to saturate Q1?

Remember that all the current through R2 will flow through the LDR when the Base voltage is below Q1s turn on threshold. After that the R2 current will split between the LDR and the transistor.

I made a new 2 LED circuit & made an interesting discovery. The new circuit works good on 2.7v. The rusted wire circuit would not work on 2.7v. Maybe rust gets deep into the wire and changes the wire resistances. Also rust from rusty wires gets on the PC board that could be making a short circuit for all the parts. Maybe if I spray new parts & board with Clear Coat it might prevent rust. I wrote 2.7v on the used batteries with 12/7/2020 date. Now I wait to see how long 2.7v batteries last and what the voltage is when they die. I made a change to the circuit, 56K resistor has been changed to 47K fixed resistor plus 10K variable resistor. At the moment total resistance is 57K circuit is working good. The original circuit had a lower resistance I change it to 56K because if a bark cloud passed in front of the sun the LEDs would flash & a cloudy over cast sky LEDs flash all day. The original circuit could have been 47K but I don't remember. 56K keeps the circuit off until about 15 minutes before total darkness. Sun has already gone down today so I will test it outside tomorrow 30 min before dark.

For the moment I have given up on the Joule Thief 1 LED 1 battery flasher the LDR will not work.

Visitor said:

TWO LEDS ON 50% OF THE TIME EACH = ONE LED ON 100% OF THE TIME.

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You must have missed where he is only going to have these on after dark, so it isn't on 100% of the time.

shortbus= said:

You must have missed where he is only going to have these on after dark, so it isn't on 100% of the time.

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The entire idea seems pointless anyway - as I recall he seems to think flashing LED's will keep burglars away

I think he uses the alternating LEDs to keep the cats away from stealing and eating his cat food dinner.
He has burglars? Oh yeah, he is in the USA. Maybe the burglars also steal and eat his cat food.

I have so many flashing LEDs that I cannot count how many. No burglars here, instead the thieves steal cars and send them back to their country.

Nigel Goodwin said:

The entire idea seems pointless anyway - as I recall he seems to think flashing LED's will keep burglars away

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So far so good. People across the street were broken into. People 3 houses down on the right were broken into. Neighbors on our left side were broken into. 3 blocks away 7 houses were broken into. Relatives had their house broken into thieves stole 80% of their food. Police told us best thing to keep thieves away are, loud barking dog, motion detector lights, security campers with red LED lights. We have all 3 and 20 flashing Red LED lights are much easier for thieves to see than 4 video cameras with 1 Red LED each. I would hate to have to shoot someone if they come into the house.

gary350 said:

So far so good. People across the street were broken into. People 3 houses down on the right were broken into. Neighbors on our left side were broken into. 3 blocks away 7 houses were broken into. Relatives had their house broken into thieves stole 80% of their food. Police told us best thing to keep thieves away are, loud barking dog, motion detector lights, security campers with red LED lights. We have all 3 and 20 flashing Red LED lights are much easier for thieves to see than 4 video cameras with 1 Red LED each. I would hate to have to shoot someone if they come into the house.

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They have got to be pretty stupid criminals to be scared off by flashing LED's - particularly ones flashing alternately

Security cameras don't even have flashing LED's on them.

Nigel Goodwin said:

They have got to be pretty stupid criminals to be scared off by flashing LED's - particularly ones flashing alternately

Security cameras don't even have flashing LED's on them.

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Thieves are stupid, that is why they steal instead of getting a job. If thieves put as much effort into a job as stealing they could make good money & not be in jail. The 2 boys that lived about 6 houses away broke into a lot of houses. Police learned who was doing it an every time another house was broken into police went straight to those boys house. The 2 boys were arrested then out of bail then breaking into more houses then got arrested a 2nd time then arrested a 3rd time. The boys were waiting for their trial day when another house was broken into. Police had dogs boys were caught 1 mile away by the dogs then in jail a 4th time. Morons never learn. Stupid morons are worse. Covid-19 has all the court rooms closed. I heard the boys are in jail with no bond Judge thinks the 2 idiots will continue to break into more houses if they are out on bond. I think stupid idiot morons are easy to fool with flashing LED lights. LOL

Flashing LEDs do not fool everyone. My security camera shows a white color car pulled into the driveway about 3pm, 2 people jumped out ran around the house trying to find a door or window that was not locked. Everything was locks so they ran back to the car and drove away. That was about 3 months ago. Police call it HIT & RUN. They run into a house grab anything of value in 1 minute then leave before anyone has time to get out of bed. Video shows car driving along the street then suddenly pull into our driveway fast then 2 people jumped out. It was all so quick I'm not sure they even saw the LED lights or even cared. I need a video camera near the street to get vehicle tag numbers. If it was not for the camera we would have never known this happened.

Political posts have been deleted. Please stick to electronics.

gary350 said:

Flashing LEDs do not fool everyone.

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get a big dog... preferably a wolf hybrid... if the LEDs don't scare the thieves away a big dog staring back at them through the window will...