Programmable Third Brake Light Flasher - PIC12F629 - Page 2 - Electronic Circuits Projects Diagrams Free

kchriste · 12th October 2007, 04:10 AM

The emitter current in the 2n2222 will be limited by the Beta of the 2n2222. This will vary with different 2n2222s. So it would be best to eliminate the 120R resistor in the base and put a resistor in the 2n2222s emitter lead instead. Choose the emitter resistor so that the TIP41 will saturate properly for the given load. Or get rid of the TIP41 and 2n2222 and replace them with a TIP121 instead.

Gayan Soyza · 12th October 2007, 04:35 AM

Hi thanks for the expert comments. It was very useful. I must work out according to the specifications given from you.

Thanks for that.

Ambient · 12th October 2007, 07:05 PM

Quote:

Originally Posted by Gayan Soyza

Hi Ambient your link is not working.I want to see that I cannot wait anymore

That is odd, the link works fine for me. You can try getting there by clicking their advertisement on hacked gadgets website: http://hackedgadgets.com/

The ad is on the left side. This guys prices are half of the next best price I can find (moreleds.com). Good customer service, too.

bananasiong · 13th October 2007, 03:04 AM

Hi,
That link worked for me too.
Back to the question, if the connection is as kchriste suggested, then where should the 1 k

hm: resistor be? Is the connection in my attachment correct?
So basically the resistor that used to prevent the leakage current from turning on another transistor is needed when there are paired transistors?

Thanks

kchriste · 13th October 2007, 05:04 AM

You have it correct, BananaSiong. The 1K resistor helps to offset any leakage caused by the 2n2222 and also any Collector-Base leakage in the TIP41 itself. While these leakage currents are negligible under normal operating conditions, they can become a problem at very high temperatures hence the inclusion of the resistor in a good design.

bananasiong · 13th October 2007, 05:56 AM

Thanks kchriste.
In the darlington pair, I see there are two resistor built in. Each of the transistor has one resistor across the base and emitter as attached.
So the 200

hm: resistor is used for the purpose that we were discussing, then what about the 5 k

hm: resistor? Same purpose? To prevent any leakage current to the base of the transistor to turn it on?

**Nigel Goodwin** · 13th October 2007, 07:39 AM

Yes, the same reason.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Title	Starter	Forum	Replies	Latest
Triac light bulb flasher	ElectroMaster	Electronic Projects	17	30th July 2008 04:20 PM
Pulsing Third Brake LIght Problem. ( whats wrong with this cct ? )	pasanlaksiri	General Electronics Chat	4	19th September 2007 07:07 PM
Need Help Designing LED Tail/Brake Light	ledsales	Electronic Projects Design/Ideas/Reviews	28	23rd May 2007 07:40 AM
MC Brake Light - Circuit Help Needed	I-See	Electronic Projects Design/Ideas/Reviews	4	16th February 2007 03:28 AM
brake light/ turn signal	andrew8485	Electronic Projects Design/Ideas/Reviews	13	11th November 2003 01:49 AM

12th October 2007, 04:10 AM	(permalink)
kchriste	The emitter current in the 2n2222 will be limited by the Beta of the 2n2222. This will vary with different 2n2222s. So it would be best to eliminate the 120R resistor in the base and put a resistor in the 2n2222s emitter lead instead. Choose the emitter resistor so that the TIP41 will saturate properly for the given load. Or get rid of the TIP41 and 2n2222 and replace them with a TIP121 instead. __________________ --- The days of the digital watch are numbered. --- Last edited by kchriste; 12th October 2007 at 04:15 AM.

12th October 2007, 04:35 AM	(permalink)
Gayan Soyza	Hi thanks for the expert comments. It was very useful. I must work out according to the specifications given from you. Thanks for that. __________________ Gayan My Website http://gsmicro.blogspot.com/

13th October 2007, 05:04 AM	(permalink)
kchriste	You have it correct, BananaSiong. The 1K resistor helps to offset any leakage caused by the 2n2222 and also any Collector-Base leakage in the TIP41 itself. While these leakage currents are negligible under normal operating conditions, they can become a problem at very high temperatures hence the inclusion of the resistor in a good design. __________________ --- The days of the digital watch are numbered. ---

13th October 2007, 07:39 AM	(permalink)
Nigel Goodwin	Yes, the same reason. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk