Simple driver circuit doesn't work

[Chrisbo]

I'm designing a kind of light sequencer, in which a 4017 counter should light up incandescent bulbs (one at a time). It works, but the bulbs glow very faintly. I guess it has something to do with the driver circuit shown below.

**broken link removed**
The transistor is a small signal BC547B (max Vce=45V, max Ic=100mA, hfe=200).

When the 4017 output is 12V, V_Bulb is only about 11V.

It's a simple circuit, so it should work, I think...

Any ideas? Would it help to have a resistance between the base and the 4017 output?

/Christian

 

[ericgibbs]

I'm designing a kind of light sequencer, in which a 4017 counter should light up incandescent bulbs (one at a time). It works, but the bulbs glow very faintly. I guess it has something to do with the driver circuit shown below.

**broken link removed**
The transistor is a small signal BC547B (max Vce=45V, max Ic=100mA, hfe=200).

When the 4017 output is 12V, V_Bulb is only about 11V.

It's a simple circuit, so it should work, I think...

Any ideas? Would it help to have a resistance between the base and the 4017 output?


/Christian

hi,
You picture posting is at fault.. can't see it..

 

[Chrisbo]

Ok, I'll try again...
**broken link removed**

Hope this is visible

/Christian

 

[ericgibbs]

Ok, I'll try again...
**broken link removed**

Hope this is visible

/Christian

hi Christian,
1. Open a REPLY window, scroll down till you see a Manage Attachments button, left click.

2. Click Browse on the new window, this open your PC files, select your image file.

3. Click Upload, wait till its done [ref progress bar on window]

4. When its done close this window

5. Make sure your file type is accepatable

Try again..

 

[crutschow]

How much current does the bulb take?

 

[Papabravo]

12V bulbs do exist but they are kinda specialized.
If you're trying to light a 120VAC or 240VAC bulb you're going to be SOL.
I didn't notice if you filled in your location.

 

[audioguru]

Why doesn't he attach the schematic here so we can see it instead of trying to post it over there where it doesn't work?

 

[Hero999]

12V is a pretty common voltage.

11V looks like what you'd expect from an emitter follower when you take into account the saturation losses.

Your tiny transistor is wasting a huge amount of power and will burn up very quickly.

 

[k7elp60]

Ok, I'll try again...
**broken link removed**

Hope this is visible

/Christian

This circuit won't work as the base has to higher than the emitter. You would be better off connecting the lamp from the collector to +24V, grounding the emitter and connecting a resistor between the base and the output of the 4017