reversed photodioded LED? help out! simple!

[Luis Costa]

i did this the other day and you know i'm just starting in electronics and was trying to do this by myself but have to come and ask the experts. How do i reverse this to get it to work as a dark light? a light that lits as much as theres dark?
Thanks

 

[AnalogKid]

Do you mean that you want the brightness of the LED to increase when the light hitting the photodiode decreases?

Also, what is the photodiode part number?

ak

 

[Luis Costa]

ty analog kid...
of course the current...
i didnt really know the current but it worked badly as its shown/ current regulated on the collector and outputing for another transistor but i guess it's helpful to bring out our stupid questions

ty for support

 

[Colin Mitchell]

How can someone so young as Luis Costa understand electronics?

 

[Luis Costa]

sorry man.... you'll get o see my face... that kid is an improved version of myself. My daughter. But yeah,... not only i'm not young - i'm 40 - i don't really know much of electronics. But i'm learning.

 

[Luis Costa]

yeah analogKid i'm struggling here. There's no numbers on the part and i've been working with currents i got from datasheets of not so similar parts.
i thing this would be the aim right?

 

[AnalogKid]

Close. The capacitor C should be replaced with a straight wire. Connect the NPN base to the PNP collector. Also, to make things easier to discuss, spread out the parts on the schematic and add reference designators (R1, Q2, etc.) to each component. Have you calculated the values of any of the components?

ak

 

[Luis Costa]

Geez man... like i said i'm testing. the first scheme works with aproximatelly those values. Now that it's suppose to be a dark light ...well...i'm trying to get around a BIAS for the NPN transistor. The output current should be of the irrelevant king for most of photodiode i checked have a current of 35uA or of the sort. but... maybe i'm wrong about the current of the photodiode. Either works or it doesnt and also i'm getting a feeling it's a small spectrum of captation. i'm not sure i'm expressing myself correctly. I'll say more later.

 

[bigone5500]

How can someone so young as Luis Costa understand electronics?

Have you never seen the Baby Geniuses movie??

 

[Luis Costa]

no FET face!!! anway this worked but 2,2M is above intended and BIAS i was thinking something like 22K but haven't tried, Also the LEDs aren't like .015A leds or anything. These need little current limitations but even if do you doesn't seem to harm the lighting purpose - hence 330R for 3 LED ( usually 1k/1k2 for LED). .