East-092 driver question: Does anyone know what the resistor does

that’s soldered in between and connecting at the base of the emitter positive and negative wires on the original East –092 driver?

I broke off one. :8)

Looking at the picture of the circuit at:


it looks like a diode. Do you have a better picture with more resolution than the fasttech site?

If it is a diode it is more than likely to keep you from reversing the battery and damaging the circuit.

batteries too often. :smiley:

And yeah, that’s exactly it alright in the FT pic.

Btw, thanks for joining today!

It’s D1 in this diagram. I think it’s a 1N5819 Schottky Diode,


maybe they should’ve been called ShockedMe Diodes. :smiley:

Good one! :smiley:

Walter may be groaning at that one! :smiley:

So I looked at the schematic that Tivo532 added here. The diode (D1) is used to prevent negative spikes from damaging the LED when the driver turns off and the current in the wires (parasitic inductance) has now where to go when the magnetic field around the wires to the LED collapse. Without the diode the LED will slowly be damaged since the reverse current will be going through the LED instead.

Why do you have to use a diode to protect a diode (a light emitting diode, in this case)?


If you look at the schematic that TIVO532 provided the LED and the diode (D1) are reverse biased with respect to each other, so that any reverse voltage across the LED is limited to the forward voltage of the 1N5819 Schottky Diode D1, which can be as low as 400mv at 100uA to as high as 1.2V at 20A. LEDs or most any diode for that mater can only take so much reverse current before they start to become damaged.

I have snipped a section of an OSRAM datasheet below. See section about reverse voltage:

I think d1 are for protect the led vs reverse polarity voltage

and the d2 are for protect the pic vs reverse battery polarity

……. but the mosfet have other internal diode for protect the mosfet vs inductive loads and this internal diode will be in series with d1 and will make a shortcircuit if the polarity of the battery are wrong

shortcircuit with reverse polarity battery: