SN 163 not working

[J Thorpe]

After initial assembly the majority of the unit worked with exception of a couple of buttons. A methodical inspection of the board and and a re-read of the instructions identified a number of resistors I had not installed, R113 thru R116. The resistors were installed and then nothing worked. At turn on I get a beep and if I push any button decimal points on the displays light up. Reading the other repair/not working threads I replaced the HT16k33A from two different sources with with different lot numbers. The behavior did not change. When I looked at the NANO pins with a scope there is no activity on any of the lines. The nano has power and the clock osc. is running . I’m not sure where to go next.

[me2016]

The missing resistors would cause the keyboard to not work but it wouldn’t destroy anything.
When you looked at the board with your scope, look at the i2c pins, they should always be busy. If not, hit the reset button on the nano an see if that helps.

Make sure that it’s no shorts anywhere, starting with the pins on ht16k33a. If you replaced the chip it may be that the new chip is from a bad version (I had to get 3 batches before I got one working).

Try to get a connection to a pc so you can see what the arduino reports on boot, remember to set the speed to 38400 (max speed for a 3.3V arduino).

If you don’t use external power, make sure the batteries are good, pref not rechargable (1.2V) but some alkaline or lithium (1.5V).

[J Thorpe]

There is no activity on the i2c lines, they stay high. The nano reset does not change anything. I will try to monitor the nano on start-up, I’m not sure how to do it but I will give it a try. The batteries are fine.

[J Thorpe]

Progress!! A friend programmed a new Arduino for me. The unit now functions. The turn on sequence seems different so I’m not sure the software is completely correct. Also, it seems to draw a lot of current, .25 amps at 3.0 volts during standby. The current jumps way up during turn on when all the LEDs come on. The unit is basically not usable with the AA cells. External power works fine. Any comments or suggestions.

[me2016]

Currently on the road but will be back next week and then I will take some measurements. I’m using it with 2 NiMH AA cells that works fine, at least when they are fully charged. Of course having 1.5v alkaline would be better.
I also plan on program an arduino and send to you but not sure if I have any spare to do that with.

[J Thorpe]

I checked the discharge characteristics of alkaline AA batteries and they should last about 2hrs at a 0.5 amp rate so the batteries should work fine, I was just surprised by the current draw. I suspect my meter is reading peak, I need one of my old VOMs to get an average reading. So far everything seems to be working OK. Every once in a while it acts funny during turn on. Then I have to turn it off and start over. I will be happy to pay for the Arduino and shipping, just let me know how much.

Thanks
J

[J Thorpe]

SN 163 is now functioning well. I did make one change that greatly improved the power issue. I went to a three cell battery holder “4.5 volts”. As expected the standby current “from the battery” is .18 amps and the peak current is significantly lower. The LEDs would dim with the audio with two AA cells they are stable with 3 cells. The 5 volt regulation is much better with the higher supply voltage. Also the battery life should be somewhat better. I am very happy with the performance now.

[me2016]

Did test a bit and yes, it takes some current.
Put my bench supply at 2.4V and it seems to take between 0.25-0.35A and spike up to 0.6A when talking. Increasing to 3V didn’t make much of a diff.
It seems to be the letters that pulls most power so M4 takes more than M3.
Moved up to 3.6V and now it’s idling closer to 0.150-0.25A. Moving to 4.5V made it take a little less.
I also noted that it in idle M4 mode it was always around 0.8W so ohms law holds, increase voltage and current goes down.
(All current values are as the bench power supply reported = may not be that exact)
Running on higher voltage is not an issue as long as it’s under 5V since it’s a booster that provide 5V to the rest of the board. Dropping below 2V was not good and while it was on at 1.2V it died as soon as any change was made.

I think going to 3 batteries instead of 2 may be a good idea and future kits may do that by default, thanks for the suggestion.

[RobertEhrenberg]

I am happy that I’ve found this topic, as my SN 162 has the same issue. I thought I soldered something bad. Everything worked fine, but the rotors were unresponsive sometimes. Also the Arduino program would hang after a few minutes.

Removing the batteries and powering the Arduino with USB-C made everything work again.

[me2016]

Another option is to go with 3 AA batteries.

[Author]

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