Adjusting nightlight

[roadtrip]

:?: I don't know much about electronics but I used to tinker a bit when I was 12. Anyway I'm a bit embarrased because I thought this might be as simple as changing a resistor in my nightlight. (the little 4 -7 watt things that you plug in to a hall socket so you can see your way to the bathroom at night). so I know what the basic parts are, but I'm a little shady when it comes to drawing a diagram. Its free hand in paint, I don't have a diagram drawing software yet. also my tester is broken so the circuit could be upside down, so beside it is the same a/c circuit upside down.

Tthe way I figured is that if I increase the value of the resister, it will lower the resistance of the voltage flow in the photosensor so that less light is needed to drop the center pin (the "gate"?) of the transistor to ground, shutting the transister off at lower light levels. See how little I know about electronics? someone please try to help this newbie who just wants to play with a soldering iron & replace a resistor) (a value suggestion might be helpful, im pretty sure its 2.2meg: red , red, green (silver,1/4 watt size) . if its more complicated, a diagram and parts list would really help because I don't want to spend a ton of money on an adjustable one or something. I can't believe it stays on on a cloudy day, I can see the hall in the day, its a NIGHTLIGHT! suggestions wecome...thanks in advance!

 

[zachtheterrible]

Depending on the way that it is set up, making the resistor a higher value might make the light stay on all the time or not stay on @ all.

Get a piece of wire and place it across the leads of the resistor. If the light gets dimmer, you know that you need a higher value resistor. If the light gets brighter, then you know that you need a lower value resistor. Placing a wire across the resistor lowers the value of the resistor greatly. i think that this'll work :lol:

 

[Roff]

It seems like there should be a diode bridge (or just a diode) in series with that circuit for it to work.
Anyhow, if you make the resistor value larger, the transistor (if it's a MOSFET) should indeed turn off at a lower light level. However, you may find that the light will flicker at night due to the fact that the light from the bulb turns the transistor off. I have had night lights that do that, especially if the outlet is surrounded by a mirror.
Shorting out the resistor, as Mr. Terrible suggested, will probably destroy your transistor and/or your photocell.

 

[zachtheterrible]

Shorting out the resistor, as Mr. Terrible suggested, will probably destroy your transistor and/or your photocell.

. i made a circuit similar 2 this one once and i shorted it out all the time . . . of course it wasnt 120V

 

[roadtrip]

Thanks guys! :lol: interestingly enough when I put the nightlight back together (for the night) I forgot to put the little plastic cover that I had popped out (right in front of the sensor) back. obviously that curved piece of plastic must block alot of light because its workin now! when I turn on my hall light or even the light off in my living room it goes out! Now all I have to do is wait for a cloudy dark rainy day....

Anyway they do flicker as they start to come on/ go off. in fact when I plugged it in it was on so I turned out the lights then turned them back on and it went out. a bit of a strange circuit?

the resistor tested at 2.37megs (red,red,green=2.2meg(+or-10%?type is silver?), & the photocell tested 1meg with a flashlight on it; all the way down to .6k (600 ohms, basically grounding the center pin of the transistor) with black electrical tape over it.

The only other solution I could think of was to tie another photocell in parralell to pick up more light & half the resistance to ground. But that would mean altering the casing..., & might make it harder to come on, it would have to be even darker.

The model I used is a GLOBE, 7.7 wattmax with a 7 watt bulb, the # on the packet is 86018 and the upc code is 58219 86018 so I guess its a 86018. it has a screw so you don't have to crack it open & then glue it back together, & it cost about $4 or$5 (I think) in Canadian cash.

A fun little project.... :mrgreen:

 

[roadtrip]

oh-oh I forgot about the dust getting on the photocell & inside. Saranwrap?