SteveL89
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Testing Gertboard

Mon Jan 14, 2013 2:26 pm

Just finished assembling my Getboard last night. I tested with a power meter, the first pin for J7 with jumper off as described. I don't get a power reading. When I test the third pin, I get 3.3 volts.

When I place jumper and run the button test and the LED test, both work properly. However, when I try to place the jumpers to get an LED readout from the button test, while the button test reads out on the screen properly, the LEDs do not light.

Any thoughts on the J7 power reading or on the buttons and LEDs?

What should I trouble shoot?

Thanks

Steve

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Gert van Loo
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Re: Testing Gertboard

Mon Jan 14, 2013 9:23 pm

If J7 pin 2 (middle pin) has no 3V3, none of the test would work.
You have working tests ergo it must have power. Where did you place the jumper?
Because the board will also work (but less good) if you place a jumper between pin 2 & 3.
If the jumper is really between pins 1 & 2 your meter could be broken or you did not have a good ground when you measured.

SteveL89
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Re: Testing Gertboard

Mon Jan 14, 2013 10:37 pm

Gert,

Thanks for your quick reply. I tested the voltage on the pin closest to the J7 and the one closest to 3v3. The one closest to J7 reads 3.3 v. The one closest to 3v3 reads less than 0.2 volts. When I put the jumper between the middle pin and the one closes to J7, everything works fine. LED and Button tests work and LEDs go on when buttons pressed when jumpers in place. When I put the jumper between the middle pin and the one closest to 3v3, the LEDs and Button tests work, but the LED lights do not go on when I press the buttons even when the jumpers are in place on the B1-B3 outs.

Steve

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Gert van Loo
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Re: Testing Gertboard

Mon Jan 14, 2013 10:55 pm

The one closest to J7 reads 3.3 v.
It had better be! that 3V3 comes direct from the Raspberry-Pi 3V3 regulator. But that regulator has only about 50mA spare.
The one closest to 3v3 reads less than 0.2 volts.
Looks like your the 3V3 regulator U1 on your gertboard is not working.
Check the orientation and if all pins are correctly soldered. No short on C3 or C1.
That one is design to give up to 500mA and should be used for normal operation of the gertboard.
When I put the jumper between the middle pin and the one closest to 3v3.....
You are overloading the 3V3 regulator on the Pi. The board is not designed for normal operation with that jumper in place.**
Anything can happen including a reset of your board.

**You can only use the jumper in that position if you know what you are doing.
E.g: Run only the motor controller. Make sure All LED's are off and the Atmega is idle.

SteveL89
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Re: Testing Gertboard

Tue Jan 15, 2013 1:39 pm

Thanks for your guidance. I checked my connections and look for a short, but I don't see anything obvious.

Just so I am clear, with the board oriented with the motor controller in the upper right hand corner when looking down at the board, J7 has three vertical pins. The bottom most pin is the one I get 3.3 volts as a reading and this is the one closest to the J7. The top most pin is the one closest to the printed 3.3 v on the Gertboard and that is the one that I don't get a reading on.

When I put the jumper between the bottom most pin (closest to the printed J7) and the middle pin, everything works as I go through the test programs including scripts to the ATmega device (Blinking and Buttons work).

However, if I understand your last post correctly, I should not jump the bottom pin to the middle pin as this can put the Pi at risk?

Thanks for all of your help.

Steve

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alexeames
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Re: Testing Gertboard

Tue Jan 15, 2013 1:55 pm

SteveL89 wrote:However, if I understand your last post correctly, I should not jump the bottom pin to the middle pin as this can put the Pi at risk?
The bottom pin, right next to J7 lettering is connected directly (via ribbon cable) to pin one on the RasPi's GPIO header. That is the 3V3 pin. You are stressing your Pi's 3v3 regulator if you connect to that one.

Just a silly thought. Is your regulator the right way round? The metal side should be facing the J7 header. If it is the right way round and the joints are OK, as Gert said above, your regulator may be faulty. This is what mine looks like...
Image
Alex Eames RasPi.TV, RasP.iO

SteveL89
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Re: Testing Gertboard

Tue Jan 15, 2013 7:08 pm

Unfortunately it is the right orientation as that would be an easy fix. On very careful inspection, it appears that the hole that the uppermost pin of the regulator is going through only has silver on one half of the hole and not the side facing the J7 pins. Could this be the problem? If so, is there a solution?

On the back of the board, the pins all look fine.

Steve

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Re: Testing Gertboard

Tue Jan 15, 2013 8:37 pm

This may be a dumb question but...

Is it possible for me to jump the bottom pin (direct 3.3 v from Pi) to a breadboard and through a voltage regulator and then back to the middle pin to supply the Gertboard?

The rest of my Gertboard works fine and I just hate to lose all that work. I certainly don't want to risk damage to my Pi though.

Steve

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alexeames
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Re: Testing Gertboard

Tue Jan 15, 2013 9:15 pm

SteveL89 wrote:This may be a dumb question but...

Is it possible for me to jump the bottom pin (direct 3.3 v from Pi) to a breadboard and through a voltage regulator and then back to the middle pin to supply the Gertboard?

The rest of my Gertboard works fine and I just hate to lose all that work. I certainly don't want to risk damage to my Pi though.

Steve
You don't want to connect anything to the bottom pin, which is connected to the Pi's 3v3. You could use an external 3v3 regulator/supply to power the Gertboard, connecting +ve directly to the middle pin between 3v3 and J7 (which feeds the power plane on the top layer of the board) and -ve to one of the GND pins. But, it would probably be wise to remove the suspect regulator in case it's shorted or something. Or better yet, just swap it out for one that works, and use that. :D

Where are you based?
Alex Eames RasPi.TV, RasP.iO

SteveL89
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Re: Testing Gertboard

Tue Jan 15, 2013 9:37 pm

I am in the US in New York.

Steve

SteveL89
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Re: Testing Gertboard

Tue Jan 15, 2013 9:59 pm

Can I test to see if the regulator itself is functioning by checking the voltage at the upper most pin of the regulator? Shouldn't that pin be at 3.3 v if the regulator is working? My concern is that the board itself may not be allowing contact to be made between the regulator and the capacitor because the pin is missing conductive material and the circuit board wiring at that site may be damaged.

Steve

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alexeames
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Re: Testing Gertboard

Tue Jan 15, 2013 10:45 pm

SteveL89 wrote:Can I test to see if the regulator itself is functioning by checking the voltage at the upper most pin of the regulator? Shouldn't that pin be at 3.3 v if the regulator is working?
Yes.
SteveL89 wrote:My concern is that the board itself may not be allowing contact to be made between the regulator and the capacitor because the pin is missing conductive material and the circuit board wiring at that site may be damaged.
You could always add a small wire or blob of solder. New York is a bit far from me (near Oxford, UK) :D
Alex Eames RasPi.TV, RasP.iO

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Gert van Loo
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Re: Testing Gertboard

Tue Jan 15, 2013 10:47 pm

SteveL89 wrote:Can I test to see if the regulator itself is functioning by checking the voltage at the upper most pin of the regulator? Shouldn't that pin be at 3.3 v if the regulator is working? My concern is that the board itself may not be allowing contact to be made between the regulator and the capacitor because the pin is missing conductive material and the circuit board wiring at that site may be damaged.

Steve
Yes,
also check the middle pin is 0V and pin 1 has 5V.
If you want to replace the regulator the best way is to cut it off.
Next unsolder the remainder of the wires one-by-one.
Then clean the holes.

SteveL89
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Re: Testing Gertboard

Wed Jan 16, 2013 3:36 am

I checked the regulator. The lowest pin reads at 5 volts, the middle at 0 and the upper pin at 3.3.

Still not getting 3.3 v (only 0.5) on the uppermost J7 pin.

I suspect an error in soldering the SMD capacitor at C1. I think the pad on which it is soldered is missing or the connection between the regulator and the capacitor is disrupted.

Any way to bypass this?

Steve

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bgreat
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Re: Testing Gertboard

Wed Jan 16, 2013 4:16 am

Good to see the regulator is OK. If the 3v3 is not on C1, then the trace may be broken between the regulator pin 3 and C1. You can solder a bare wire from the regulator to top of C1. The scrap from cutting off an LED leads would be a good choice. Make a good solder connection on both ends keeping the wire flat to the board. Be careful to not short to C3 or the center pin on the regulator.

Enjoy!
Bill

SteveL89
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Re: Testing Gertboard

Wed Jan 16, 2013 4:44 am

Bill,

Is the regulator pin 3 the top most or bottom most pin? It looks like the trace at the top most pin may be the problem.

Steve

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Gert van Loo
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Re: Testing Gertboard

Wed Jan 16, 2013 8:32 am

Top most pin. (Assuming board is oriented so the text is readable).
All printed circuits board are supposed to be electrical tested after manufacturing.

SteveL89
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Re: Testing Gertboard

Wed Jan 16, 2013 11:04 pm

Thank you all for your advice and help. I fixed it!!

Here is what I did. I took Bill's advice and cut the lead from an LED and soldered it from the C1 capacitor to the top pin of the regulator. I tested the voltages and still, nothing for the top pin (the one closest to the 3.3v printing or the uppermost pin). On closer inspection, it was clear that the pad is missing from the top connection of C1. I must have screwed it up when I was soldering the surface mount components. When I tested voltage at C1 it was now 3.3 so I knew I had jumped successfully from regulator post 3 to C1. Now all I needed to do was jump C1 to the top pin. I made a small loop at the end of a cut wire and put this around post one and soldered it to post 1 and then to C1. This did the trick. Now the uppermost pin reads 3.29 v. Middle pin still 0.2. I then put the jumper between the top and middle pins and the board now works.

Hopefully I did this right and all is well.

Thanks again.

Steve

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alexeames
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Re: Testing Gertboard

Wed Jan 16, 2013 11:35 pm

Yay. A happy ending. :D Enjoy playing with it now. :)
Alex Eames RasPi.TV, RasP.iO

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bgreat
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Re: Testing Gertboard

Wed Jan 16, 2013 11:43 pm

:D Great!

A little late, but instead of looping around the header pin, you can scrape the solder resist off to expose the trace and solder directly to the trace that goes under the header to the pin.

I loved building my Gertboard! Just wish it was still available as a kit. MCM sold out again before I could order. :(

Enjoy!
Bill

SteveL89
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Re: Testing Gertboard

Wed Jan 16, 2013 11:54 pm

I thought about doing that but was worried I might muck it up and there is not much space between the components.

A bit jury rigged I admit, but it seems to be working fine and hopefully now the voltage regulator for the Pi is no longer in play and I won't get any resets.

Working my way through the Gertboard test programs now.

Thanks again! :D

Steve

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