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UForce sensor problem?
Posted: Wed Oct 08, 2014 10:07 pm
by DrDementia
Hi I got a uforce but one of the sensors isn't working(top left sensor). I tested with the uforce test cart in analog mode(first 3 switches down)and all the sensors seem to work except that one.
I looked at the emitter with a camera and it(and others) light up. Not sure how to test this thing, I have a multimeter. There should be a spot I can bridge that bypasses the detector. Not sure if its the wiring or what.
This thing is a mess inside. the only info I could find is here.
http://blog.kevtris.org/blogfiles/nes/uforce.txt
I don't think there's any pics of the insides. here's a couple
***warning they're big
Anyone have any ideas?
Re: UForce sensor problem?
Posted: Wed Oct 08, 2014 10:33 pm
by lidnariq
The nice thing is that those are infrared reflectance meters... they usually only have a range of a meter or so.
The black ones should be the ones that emit IR; the clear ones would then be phototransistors. Do you have a multimeter? You should see a comparable voltage across the phototransistor when a comparable amount of light is shining on it, so you can compare the bad pair to other ones.
Re: UForce sensor problem?
Posted: Thu Oct 09, 2014 9:24 am
by DrDementia
yeah the black ones(emitter) I can see IR light with a camera.
yes as I said I have a cheap multimeter.
I'll use kev's diagram to help explain the readings.
(top)
/------sensor 1-------\
|----------------------|
|sens. 2------sens. 3|
|----------------------|
|----------------------|
|sens. 4------sens. 5|
|----------------------|
*****************
here's my voltage test, tested both parts. (#2 is the one not working correctly)
E=emitter P=phototransistor D=what the reading is when I shine a led flashlight into P. the voltage drops. Values are rounded.
#1
P=440
E=150
D=050
#2
P=290
E=120
D=050
#4
P=295
E=140
D=050
#3
P=260
E=060
D=025
#5
P=265
E=120
D=050
Re: UForce sensor problem?
Posted: Thu Oct 09, 2014 12:37 pm
by lidnariq
Huh. That strongly implies it's not the sensor that broke.
Maybe one of the wires? The ribbon cables look kinda fragile.
One of the transistors (TO-92 black plastic "D" things) could be toasty? It might be a Sziklai or Darlingon pair amplifying the signal out of the phototransistor.
Re: UForce sensor problem?
Posted: Thu Oct 09, 2014 2:17 pm
by DrDementia
yeah it seems to be working.
I suspected it might be the wire from the uforce to the nes. I was hoping it was the emitter or detector maybe I could have just swapped them.
I guess I'm going to try to trace the board and check it farther back that might rule out the ribbon cable. If anyone's interested I can take some more pics of the boards.
thanks for the help so far. I'm open to ideas.
EDIT: I did a continuity test of all the ribbon cables, and from the uforce to the plug. Everything seems fine. that rules that out.
must be one of the components
Re: UForce sensor problem?
Posted: Fri Dec 05, 2014 4:08 am
by l_oliveira
So many resistors are cut and have one side lifted... Is that a factory made modification ?
Re: UForce sensor problem?
Posted: Sun Dec 07, 2014 10:39 am
by Quietust
l_oliveira wrote:So many resistors are cut and have one side lifted... Is that a factory made modification ?
Based on kevtris's reverse-engeering document (linked in the original post above), yes:
To "calibrate" the sensors, they had groups of no less than 8 resistors in parallel. To perform the "calibration", they would cut out some of the resistors! As you can imagine, this is a mess. Some of the resistors had been re-soldered and re-cut in cases to make it operate properly. I fully traced the circuitry of this thing out and I cannot believe it functions. The design is pretty terrible and needed alot of hand tweaking to make it function, as evidenced by capacitors (up to three) paralleled in places. The caps range in value from 50 to 100 pf or so. These things must have been a nightmare to make in any kind of production volumes due to all this hand tweaking required.
Re: UForce sensor problem?
Posted: Sun Dec 07, 2014 1:04 pm
by tepples
Perhaps they heard pot was illegal and thought it meant
trimpots were illegal too.