Do I have a bad board?


Just got the orangutan board a few weeks ago.

I followed the instruction and connect a 9v battery
with a clip to connect to the board. Here is
my setup for the power connector:

* power led

[ ] +9v
[ ] ground
--------------- <-- bottom of the board

Turn on the switch by pushing downward. Nothing
happened. No power led.

When the switch is off, I get around 9v across JP3 (header2).
However, when I turn the switch on, I get around
1.2v. Vcc is around 0.7v.

Is the board bad? I have been tracing the schematic
for a few hours and still could not find the problem.

Upon examining the circuit, it seems there is a
thin strip of wire shorted across some pins for the lcd
(see the following diagram). Is this by design?

Figure: Bottom of the board (pins of lcd. Short between
fouth and fifth pin)

    ^ ^ ^ ^ ^ ^ ^ 
    ^ ^ ^ ^-^ ^ ^ 

I think it will make it easy to trace the circuit
if you also provide a diagram showing the placement
of the parts.


Sounds like something is shorting somewhere alright, but I’ll wager that the “thin strip of wire” you’re seeing between those pins of the LCD header is actually a 4.7Kohm resistor (you can check this with a multimeter):

-(thanks for the pic Jim!)

This is a modification made to the later (black bezel LCD screen) to keep the newer screens from interfering with the programmer. If you’re interested you can read all about it in this thread

Actually, do you have a multimeter around? You could use a continuity checker to see if there is a short between Vcc. It might not even be a total short, you could have a low resistance connection, or a backwards diode. Anyway, whatever the problem, its clear that somethings amiss.



Do you have anything connected to the 5V line? The power switch only switches the power to the 5V part, and 0.7V sounds a lot like a forward diode drop. The units are all tested prior to shipping, and I’m quite confident that nothing happening on power-up would have been caught. If you aren’t able to track down the problem, you can send it back for us to look at (contact us first for an RMA number).

By the way, most of the technical staff will be in Seattle (for Robothon) from tomorrow until Monday, so unfortunately, we won’t be able to help much until Tuesday.

- Jan

Thanks for your responses. I really appreciate
for your help. The thin strip of wire turns out
to be a resistance. I guess I need my reading glass.

I have not connected anything to the 5 volts.
I was just trying to power up the board and nothing
shows up.

I will try to troubleshoot this weekend.

Just wonder if you have diagram showing the placement
of components. I am not familiar with surface
mount components. I am a software guy doing robotics as a hobby. :smiley:

After some troubleshooting, I have found
the problem. But, it really made me feel

It has nothing to do with the board which works

The problem is with the solder in my home-made
battery clip which has a 47K resistance on the
positive side. Basically I have a voltage divider.

Sorry for wasting everyone’s time. But I did learn
a lot from tracing the circuit.

Thanks again for everyone’s help. I am trying to
demo your board in the upcoming robot club meeting.