K7302

Hi,

A few time ago I bought an universal battery charger, I did the soldering and stuff. But my problem lies with the schematic diagram.
I understand the use for the Diode D1, and the capacitor C1. But I don’t know what’s the use for the 2 resistors and the transistor. I don’t see the link between them. So I called Velleman, and they said I had to ask it here, on the forum. So I hope that someone is able to answer my problem.

Thanks, Matthias

[quote=“matthias”]Hi,

A few time ago I bought an universal battery charger, I did the soldering and stuff. But my problem lies with the schematic diagram.
I understand the use for the Diode D1, and the capacitor C1. But I don’t know what’s the use for the 2 resistors and the transistor. I don’t see the link between them. So I called Velleman, and they said I had to ask it here, on the forum. So I hope that someone is able to answer my problem.

Thanks, Matthias[/quote]
Hi Mattias,
The transistor T1 functions as a “constant current source”. Is does what its name says: it delivers a constant load current to the battery independant (within certain boundaries) of the supply voltage on C1. The current is given by: (VLD1 - VbeT1) / R2.
In the illustarted assembly manual there is a table with the R2 versus load current relation.