4 pin EDU PWM out power, red pin2 V in error
 

Our EDU controller measures 7.2V(to ~8v charged) on both pins 2 & 4.
Pin 2 (red) should be +5v
Pin 4 (unk color) should be 7.2v

Has any other teams observed this problem ?

I was looking for but find no jumper option
(so servo's could use either unreg or reg)

We could have a fault/failure inside the EDU +5v power distribution.

The middle digital IO pin does properly read +5v
(have been using that until problem is resolved)

anyone know if there are separate +5 regs inside EDU ?

Any ideas what the problem is ? or Do other EDU's have it too ?

Beacons w/7.2v to 8V charged,
using this fault would start our ~2X brighter
8v-1.34/33ohms=.2A
where orig design=5v-1.34/33 =.111A

(note IR LED's were tested, forward V=1.34v at .11A dc)

Re: 4 pin EDU PWM out power, red pin2 V in error
 

Nope, both pins should measure +7.2v ( the current voltage of the battery)

See the EDU referece guide http://www.innovationfirst.com/FIRST...2003-11-14.pdf

Re: 4 pin EDU PWM out power, red pin2 V in error
 

Thanks for the quick reply RD.

So was the FRC Beacon LED current designed for ~202 mA ea?
(Ipk =8v-1.34VfwdIRled)/33ohms)

and decrease in IR output intesnity as the battery voltage declines ?

A previous poster indicated red EDU PWM = 5v where
Ipk = (5-1.34)/33 = 111 mA each of 4 parallel LEDs ???

Re: 4 pin EDU PWM out power, red pin2 V in error
 

OH CR...UD! Mea Culpa, Dude. I'm sorry, you were correct and I laid down a healthy dose of... Er,... Well, you know. Anyway, the LEDs should be okay (I've driven them up to 800mA with the beacon waveforms), but now I'm somewhat worried about the power rating on the resistors. Some teams got 1/2 watt, but as I found out a few days ago, others got 1/4 watt (ouch!). I guess I'll add an entry to the FAQ addressing the resistors (which may be another good, but unintended, source of infrared energy :ahh: ).

-Kevin

Re: 4 pin EDU PWM out power, red pin2 V in error
 

Kevin,
retraction appreciated, Thanks

There should be no problem with 1/4 W resistors
pulsed 40kHz & 1-2mS burst
(5% overall duty 1mS 40 pulses 50-50 & 10% 2mS 80 pulses)

WC .2A^2*.1duty*33 = .132W ~53% utilization of quarter Watt resistor.

at least not until they are accidently driven w/DC. (EDU pgm croak)

.2A^2*1duty*33 = 1.32W ~5X that quarter Watt resistor
that unmistakable smell of carbon burning, ahhh

that makes my proposed 4x LED series string + 1 current limit resistor
(or 2 junct tran+resistor regulator)
(5.36v from 7-8 Vbatt) look a bit better. least on paper.

We'll have to deal with the IR dropoff with dwindling battery supply,
or use an AC adapter, not a big deal.