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parsaver
07-30-2014, 03:00 PM
Ever read so much you get your self even more confused than when you first started?

I'm working on a Graflex with a PCv3 and a RB/RB/Wh Tri-Rebel of a 14500 2 pack. I have been reading through the manual and was looking online for the 2512 2W SMD resistor to put in for the white die when I read in the manual the example resistor calculation.

For those who haven't seen it, it looks like this:

Required resistor for the FoC circuit :
R = (Vpack ? Vf die) / FoC current
R = (7.4 ? 3.7) / 1 = 3.7 ohm

Wattage of the resistor :
P = RxI2 = 3.7 watt.

This makes perfect sense to me (V/I=R)as there are two 3.7V batteries running the board. From what I can see, the Vf of the white die should be 3.2 so I should have a 4.2ohm resistor. easy as pie.

And below that Erv says:
Since the FoC circuit is only active for a short time (maximum 10 seconds during a
lockup), it?s acceptable to use a 2 or 3W resistor in the example above.

So I can get away with using a lower watt resistor. Good to know

But then it says:
If the user wants to drive an accent LED out of the FoC pad (and not a high-power
LED die), this can be of course achieved without a Power Xtender board, just like any
accent LED. The pad outputs 3.3V and 18 mA maximum.

this is where I get turned around.

Forgetful Jedi Knight has a wiring diagram but it has the PEx on it.

Wait....I thought the PCv3 eliminated the need for a FoC or PEx satellite board? According to every diagram I can find, the +power comes from the battery+ pad and should be 7.4V where as the negative(-) LED wire connects to the resisted part of the FoC Pad. Where is this 3.3V pad at? SO I can drive the white die FoC LED from one FoC pad and use an accent out of the other? The more I search the more confused I get...

Then it says:
If you want to activate one channel during the Flash On Clash effect, set the
channel "current" to the max (1500). Lowering the value will adjust the drive of the
FoC but it will make the onboard Power Extender act as a resistor and it will absorb
some of the heat. However, a drive adjustment is not recommended most of the time,
let it to the max and adjust the value of the 2512 resistor instead.

So there is an onboard power extender and I should adjust my resistor calculations for 1500mA instead of 1000mA?

Am I over thinking this? Should I just buy a 3 Ohm/3 Watt 2512 and solder it into the "green rectangle" from the manual?
Any clarification or simplification out there?

Forgetful Jedi Knight
07-30-2014, 03:18 PM

Ever read so much you get your self even more confused than when you first started?

I'm working on a Graflex with a PCv3 and a RB/RB/Wh Tri-Rebel of a 14500 2 pack. I have been reading through the manual and was looking online for the 2512 2W SMD resistor to put in for the white die when I read in the manual the example resistor calculation.

For those who haven't seen it, it looks like this:

Required resistor for the FoC circuit :
R = (Vpack ? Vf die) / FoC current
R = (7.4 ? 3.7) / 1 = 3.7 ohm

R = (7.4 - 3.2) / 1 = 4.2 Ohm

Wattage of the resistor :
P = RxI2 = 3.7 watt.

4.2 * 1^2 = 4.2 W round up to 5W

This makes perfect sense to me (V/I=R)as there are two 3.7V batteries running the board.
From what I can see, the Vf of the white die should be 3.2 so I should have a 4.2ohm resistor. easy as pie.

And below that Erv says:
Since the FoC circuit is only active for a short time (maximum 10 seconds during a
lockup), it?s acceptable to use a 2 or 3W resistor in the example above.

So I can get away with using a lower watt resistor. Good to know

True, as long as you strictly adhere to the limits. Padawans RARELY adhere to limits. Erv' is also talking about using the PC onboard pads. ALSO a big difference. Ideally you do not want the board getting overheated because it will start to act funny, and you'll be back complaining about whatever it is. I'm saving you the complaining step. ;)

But then it says:
If the user wants to drive an accent LED out of the FoC pad (and not a high-power
LED die), this can be of course achieved without a Power Xtender board, just like any
accent LED. The pad outputs 3.3V and 18 mA maximum.

Doesn't apply to you unless there is something you haven't told me.

this is where I get turned around.

Forgetful Jedi Knight has a wiring diagram but it has the PEx on it.

Wait....I thought the PCv3 eliminated the need for a FoC or PEx satellite board? According to every diagram I can find, the +power comes from the battery+ pad and should be 7.4V where as the negative(-) LED wire connects to the resisted part of the FoC Pad. Where is this 3.3V pad at? SO I can drive the white die FoC LED from one FoC pad and use an accent out of the other? The more I search the more confused I get...

It does as long as you adhere to the strict limits stated above by Erv'. Since you don't want to have problems in the future, I am giving you the "safer" way to handle your wiring. ;)

Then it says:
If you want to activate one channel during the Flash On Clash effect, set the
channel "current" to the max (1500). Lowering the value will adjust the drive of the
FoC but it will make the onboard Power Extender act as a resistor and it will absorb
some of the heat. However, a drive adjustment is not recommended most of the time,
let it to the max and adjust the value of the 2512 resistor instead.

So there is an onboard power extender and I should adjust my resistor calculations for 1500mA instead of 1000mA?

No, use 1000 mA because not all LEDs can run at 1500 mA, unless you want to blow up your LEDs. Rebels run at a max of around 1000 mA NOT 1500 mA

Am I over thinking this?

YES.

Should I just buy a 3 Ohm/3 Watt 2512 and solder it into the "green rectangle" from the manual?

NO.

Any clarification or simplification out there?

You need something along the lines of a 4.7 Ohm 5W resistor (see calculations above). You can use the big honking resistor (4.7Ohm, 5W), or you can use the PEX and an SMD resistor(s). Choice is yours.

parsaver
07-30-2014, 03:30 PM
You need something along the lines of a 4.7 Ohm 5W resistor (see calculations above). You can use the big honking resistor (4.7Ohm, 5W), or you can use the PEX and an SMD resistor(s). Choice is yours.

To confirm,
So just bridge the FoC pads (green square in the manual) and wire the big ceramic one up inline....which I don't think it will fit. "it's gonna be close..."

or

the SMD on the bottom and don't mess with anything else it its going to over heat and possibly malfunction

If I use the PEx I still need it resisted anyway, with the big ceramic one?

Forgetful Jedi Knight
07-30-2014, 03:34 PM
To confirm,
So just bridge the FoC pads (green square in the manual) and wire the big ceramic one up inline....which I don't think it will fit. "it's gonna be close..."

or

the SMD on the bottom and don't mess with anything else it its going to over heat and possibly malfunction

If I use the PEx I still need it resisted anyway, with the big ceramic one?

OR bridge the onboard pads, use the PEX, and you can use small SMD resistors if you get the right ones on the PEX. It'll save you the space which you doubt you have and which is on of the reasons why I suggested it to begin with. ;)

parsaver
07-30-2014, 03:43 PM
Stop with the logic!! :)

Where is the best place to get the SMD resistors? Newark?

Forgetful Jedi Knight
07-30-2014, 03:44 PM
Stop with the logic!! :)

Where is the best place to get the SMD resistors? Newark?

Correct.

parsaver
07-30-2014, 03:53 PM
In case no one told you today...you da man!

Thanks for the help.

setelf3of5
09-05-2014, 02:00 PM
OR bridge the onboard pads, use the PEX, and you can use small SMD resistors if you get the right ones on the PEX. It'll save you the space which you doubt you have and which is on of the reasons why I suggested it to begin with. ;)

In the above example is the resister a 2512? And since this is an old post where can the SMD resisters be obtained now?