2.2v to 5v

[mister_e]

let's do some calc to see what happen...

Ic(T1)=(12/10,000)=1.2mA

Ib(T1)=(3/22,000)=0.136 mA

a Hfe minimum will be Ic/Ib = 8.8 to make this work. it's usual and recommended to multiply the minimum Hfe by 5 or 10. so here between 45 and 90 will be the minimum.

Looking at BC237 datasheet, Hfe min = 120, so it has to work.

And yes i forgot to add some extra load at first calc. But you get the idea.

[joseph Degorio]

Thanks Alain and Steve...appreciate the help, I will post back the update as soon I get to work with my project this weekend.


Regards,
Joe

[Ioannis]

If I may ask, why don't you use the ULN2001 that has no base resistor and a min Hfe of 1000? You can calculate the external resistor if necessary or connect directly to the low voltage output of the PIC you use.

No additional transistors. Just a resistor, but I think is not necessary anyway.

Ioannis

[joseph Degorio]

Hi everyone,
Again thanks for the reply and the effort for helping me out. Thanks to Alain for his schematic because I got it to work. To be honest I found out later on that by removing the LED between the I/O and ULN2003A gave me the 5v needed for input to the 2003A which solved my problem... anyways I guess I'm learning new things...


Thanks all,
Joe