Hello, I'm Sid and I'm currently in the process of doing my GCSE coursework. The project I am doing is a solar mobile charger. Although I have found very easy circuits to use, my electronics teacher said I needed more challenging process components, so I have combined a simple circuit with a more challenging circuit using an IC 555. Here are the links to the said circuits.


Challenging IC 555 circuit


PARTS LIST
Resistors (all ¼-watt, ± 5% Carbon)

R1 = 390 Ω

R2 = 680 Ω

R3 = 39 Ω/1W

R4 = 27 KΩ

R5 = 47 KΩ

R6 = 3.3 KΩ

R7 = 100 Ω/1W

VR1, VR2 = 20 KΩ

Capacitors
C1 = 0.001 µF (ceramic disc)

C2 = 0.01 µF (ceramic disc)

C3 = 4.7 µF/25V (Electrolytic )

Semiconductors
IC1 = NE555 timer IC

T1 = SL100 or any Medium power general purpose NPN transistor like: 2N4922 , 2N4921,2N4238, FCX1053A

ZD1 = 5.6 V/1W

LED1

Miscellaneous
SW1 = On/off switch

1.5V*8 AA cells

Mobile connector




And then the simple solar charger



My combination of the two circuits using circuit wizard





The phone battery will be connected in series between the cathode of D3 and ground. The filament lamp there was my attempt to represent a charging battery. The IPhone charging requirements are 5v and 250-500mA but as you can see, I'm only getting ~1v and 162mA and I am not able to understand why. It seems that the higher current draw a component possesses, the lower the voltage drops. If anyone could help me here it would be greatly appreciated and if anyone has any improvements it would be of great help (keep in mind I must keep the 555 IC). V1 and V2 are just representing the solar panels. The transistor model is set to "Ideal" on circuit wizard on my circuit.

Links to the webpages/sources I used for my circuits.
http://www.techulator.com/resources/10562-Make-your-own-Solar-mobile-charger.aspx
http://electronicsproject.org/mobile-cellphone-charger/

 

On your bottom diagram your feeding the 555 with 5V, yet you have a 5.6v zener on pin 5, why?

 

On your bottom diagram your feeding the 555 with 5V, yet you have a 5.6v zener on pin 5, why?

I thought when we use zener diodes it must have a slightly higher tolerance than the input voltage

 

Pin 5 of the 555 chip is the 2/3 control voltage, all you are doing is lowering it from 8V to 5.6v, so if you supply the chip with 5V, the zener is obsolete.

You're using the 555 as a comparator, personally i would use a window comparator using a Lm358.

 

I

Pin 5 of the 555 chip is the 2/3 control voltage, all you are doing is lowering it from 8V to 5.6v, so if you supply the chip with 5V, the zener is obsolete.

You're using the 555 as a comparator, personally i would use a window comparator using a Lm358.

I will consider that, but is there any way to get by using a 555? Thanks for the help by the way.

 

It will work if you supply the 555 with12v, like the top drawing.

 

It will work if you supply the 555 with12v, like the top drawing.

Originally I had the 555 circuit first, then the small voltage regulator circuits but that had the same problem where when I increased the current draw of a component, the voltage dropped