11 thoughts on “PopSci Hack-O-Lantern

  1. Mr Ragan leaves the light sensor tightly attached to the breadboard. As EMSL showed a couple of years ago, the better way is to put the sensor on a lead (say a foot long), then have the sensor stick out a little from the pumpkin cap after it’s closed. That way you’re really measuring ambient light.

  2. I just built this thing, and although it works, it is very dim (even in total darkness). I used a multimeter to check the current going through one of my LEDs, and I was only getting about 1.5 mA. Any ideas as to what the problem might be?

    1. Got it. Flip those NPNs around. The LEDs now need a much darker room to turn on, but when they do turn on, they are significantly brighter.

  3. I’m with Burt. I have a background in electronics and am surprised anybody could build this w/o a wiring diagram.

  4. I’ve been working on this on and off for a few days and haven’t been able to get the phototransistor to turn off the lights, any advice? The LEDs turn off if I split the positive wire and connect one end to where the phototransistor emiter should go, so I’m pretty sure everything else is correct. Also I really can’t tell from the photo which resistor is the 5-kilohm resistor though think it’s the bottom left one, is that correct?

    1. We don’t normally provide support for other folks circuits. I’d suggest contacting Sean for assistance, and double checking the orientation of your transistors and phototransistor.

      1. I finally got it to work when I switched out the transistors for some meant for lower voltage; initially I was using transistors rated to 12v and I don’t think they allowed enough current to pass at the lower voltage.

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