Driver transitor for LED emergency light

RizF1 said:

Hi

My knowledge in electronics is limited. I built this circuit.

I had a problem. The variable 2k2 has one point on negative and other point and middle point common with adj LM317 and collector of BC548. When i do this bridge, capacitor and LM gets really hot.

Then in changed and made on point of variable on negative other point on adj of LM317 and middle point on collector of BC548 and everything worked perfectly OK.

Am i reading the schematic wrong or what?


Secondly we are having 6-8 hrs loadshedding (power cut) per day in our country and my 6v 4.5AH battery gets fully charged in 20 hours, can i make some changes to it so that it can charge in just couple of hours?


Thanks

Click to expand...

wasrana said:

Hi


I've built **broken link removed** circuit for LED emergency light which turns the LEDs on when there is power failure.

It use BD140 pnp transistor for this purpose. I have 60 LEDs in the panel which are best operated at 3.25 volts drawing 950 mili amps.

BD140 only gives 3V and max current of 450 milli amps (without any resistance attached to LEDs) so the LEDs don't glow as bright as they should.

I tried BD176 but the results were worse then before i could only deliver 250 miliamps (without any resistance)

I then trided TIP42c, it gave 650 mili amps @ 2.98 volts without applying any reistance.

What would be the best transistor in the circumstances which could deliver the desired voltage and current.



PS: My knowledge in electronics is just basic.


Thanks in advance
Waseem

Click to expand...

mneary said:

The circuit does have a flaw; the transistor base bias assumes that the voltage across C1 goes 'low' when the power fails. But the only load on it is the no-load current drain of the LM317. I would add a 560 ohm 1/2-watt resistor across C1, and would change R15 to 270 as well.

And of course I would use the LED resistors as shown in the original circuit. Why leave out resistors? Do you prefer building things that don't work?

Click to expand...

irfanulla said:

HI as again - this is the first post and I have been searching for a circuit since I have a strip of LM317HV's and a few transformers lying around -

what would be the quick charging method - is it pumpin in more current or more voltage?

I am a mechanical engineer and low on electronics knowledge - but this circuit is very interesting and I wanna build this ASAP - again there are so called fast chargers in the market - what do they actually do to get the batteries charged faster - I have read else where that we need 1/10 th of the rated current of the battery to charge it - how much time does it require that way, also how do we calculate the estimated backup it can provide.

RGDS
IRfan

Click to expand...

RizF1 said:

Hi

My knowledge in electronics is limited. I built this circuit.

I had a problem. The variable 2k2 has one point on negative and other point and middle point common with adj LM317 and collector of BC548. When i do this bridge, capacitor and LM gets really hot.

Then in changed and made on point of variable on negative other point on adj of LM317 and middle point on collector of BC548 and everything worked perfectly OK.

Am i reading the schematic wrong or what?


Secondly we are having 6-8 hrs loadshedding (power cut) per day in our country and my 6v 4.5AH battery gets fully charged in 20 hours, can i make some changes to it so that it can charge in just couple of hours?


Thanks

Click to expand...

Boncuk said:

Hi to all interested in building the circuit,

I have designed a PCB including the changes as suggested: 560Ω/0.5W resistor across C1 and base resistor of T2 reduced from 1KΩ to 270Ω. Additionally I put four 47nF capacitors across each connection of the bridge rectifier. (makes the LM317 happy) The transformer used is a Gerth print transformer type 421.1-9 with max 556mA.

The entire design is purely single sided.

The design can be used as one single board or might be split into two as outlined in the dimension drawing. Connections between boards are marked A-A1 and B-B1.

Everybody interested in the layout (and schematic) is welcome to obtain it free via email. It is made using Eagle v. 4.16.

Here's a screenshot of the board.

Regards

Hans

Click to expand...

rrayamajhi said:

I kindly request you to send me PCB layout for emergency LED light.

Thank you

Rajan
rrayamajhi@yahoo.com

Click to expand...