The parallel combination of 8 LEDs is 8x 20mA - if your BD140 can handle that current, it will do so if you modify for 12V.Hi Everyone,
I'm thinking of making this circuit for a project for a friend new letter box, to illuminate with Leds over letterbox numbers.
I want to make this circuit in 12 volts version.
I will upgrade the following:
Solar Panel to 12 volts @ 10 Watts http://www.rpc.com.au/catalog/cnpv-12volt-solar-panel-10watt-p-2701.html
Battery 12 volts @ 15Ah
I will change the BD140 for TIP32 as the TIP32 is to energised a 12 volt 3 Amp relay, as I'm running more Leds then below.
Do need to beef up the circuit anywhere else.
Any help would be greatly appreciated
The TS wants to convert to 12V - at the stated 3.6V per LED, you can just about get away with 3. That comes to 10.8V, which is the absolute minimum discharged voltage of a lead acid battery (many texts advise not discharging below 11.5V).The most per leg you can get with 3.6V Vf LEDs is 3 LEDs, so that would be a total of 18 LED legs.
With a joule thief arrangement the least you can use per leg is 4 LEDs, which is why I used what I did.
Unless there's a whole new breed of white LEDs out there that I haven't heard about I think that's a typo in the spec .Forward Voltage (V): 1.6-2.1V
If you have them on the bench, use a suitable limiting resistor with an LED for say 20mA and measure the forward drop, 'W' will need to know the actual value.Well I'm only going by what the seller on Ebay specified! Must be 3.1 Volts!!