switching Vss with a transistor

B

bryanwilkerson 18 years ago

Total hobbyist here.

Is there anyway to wire a transistor so that it closes the Vss instead closing the connection to ground?

I have a ciruit like this

Vss --------R1----+------------+ | | 3000 uF LED | | gnd --------------+-------------+

The capacitor provides a nice fade when Vss is switched off which is much more cool than just blinking.

So i need to wire this into the output of a sound actuation circuit (already done). But in order for the sound actuation circuit to drive the heavier load (100s of LEDs), I added a transistor.

This is how I see it done in my books and online

formatting link

but the problem is that the LED never gets the current bleed from the capacitor because the transistor switched off connection to ground. The other way around would work:

+5V in | Vss ----T1--R1----+------------+ | | 3000 uF LED | | gnd-----------------+------------+

But the transistor I'm using doesn't seem to want to work in this configuration.

Any ideas?

Vote

L

linnix 18 years ago

Use a load switch.

Vote

J

John Fields 18 years ago

First, when you\'re drawing ASCII schematics, use a non-proportional font like Courier and _never_ use the TAB key, use the space bar. Second, try this: (View in Courier) +V | [R] | +-----+ |A |+ [LED] [BFC] | | +-----+ | C ACT>--[R]--B NPN E | GND But, _hundreds_ of LEDs???

Vote

switching Vss with a transistor

Join the Discussion

Didn't find your answer?