Narrow-Bandwidth Television Association

Just for the record, the Arduino auto - detects if there is a Lcd present, and if not then it will auto - play all of the videos on the SD card in an endless loop.

Hi Andrew, here is the feedback on the PCB as promised and my recommendations if you were to do a respin

Modifications chosen for my build.

Only one switchmode power supply is needed. What was really needed was capacitors to get rid of power supply and light source noise. Here are the mods I did to make this a one power supply solution using a standard 12V laptop style brick to supply the power.

1) Fit a 2.5mm jack as everything uses this and it can be unplugged
2) Remove the 7V powersupply on PCB
3) Remove the 12V powersupply on PCB
4) Jumper 12V to 15V where 12V powersupply was.
5) Fit a 470uf 25V capacitor across the 12V where the 12V power supply was
6) Fit a 470uf 25V capacitor across the 12V where the 7V power supply was
7) Fit 2 x 470uf 25V capacitors directly across the main motor.
Jumper the powersupply 5V out to the 5V pin on the Arduino
9) Add 47uF 16v capacitor acrros the 5V and ground on the Arduino
10) Added 4 pin connector for optocoupler. Used standard stepper motor pre made cable
11) Added socket for Arduino in case I needed to replace it.

Possible Improvements
1) Connect the flood plane to gnd
2) Label the sensor pin long lead/short lead instead of plus minus
3) All pad annular rings are small. Rule of thumb is make them a big as possible unless forced to go smaller
4) Make speaker a 2 pin 100mil pitch Arduino plug
5) Make some 3mm mounting holes with clearance for screw heads etc

TX and RX on the TFT are correctly labeled, do not change. There is a sneaky 10K pull up on the SD card if you look too.

And some pictures of the mods





Cheers
Keith

Interesting,
I see you are saying 2 x 470uf 25v Electrolytic's across the motor. Forgive my ignorance in asking this, they are soldered in parallel + to + correct?

The next question is I see a 1000uf 25v Electrolytic on (the site that I will not mention) is that equivalent (close enough) to replace both your 470uf 25v or is that the wrong way to look at it?

My DC motor is 12v, would either of these work?

Sorry to ask, I know its my problem, not yours.

It really doesn't matter too much. i just had two 470s that in parallel make about 1000uf. You should just pull the parts out of some junk which saves buying and waiting for them. I scoped the signal and added capacitors until the noise went away. And yes it works perfectly with PWM. Basically it takes all the nasty PWM and commutation noise away. And yes 25v or higher is ideal for 12v

The most important thing is don't put them in backwards or they might go boom! haha. Stick them directly on the back of the motor for best performance.

Cheers
Keith

Two 470uF caps in parallel should be fine to replace a single 1000uF unit. Remember most electrolytics have a wide tolerance of +80/-20% anyway. That's when new, if sitting on the shelf for a while (years) or recovered from used gear the variation could be even greater, though more than likely on the decreasing side.

Although it usually will not apply to NBTV or gear used in a domestic setting, electrolytics lose much of their capacitance at low temperatures, though in automotive applications it does apply. Think of Northern Sweden or Canada in winter. At -20C as much as 75% of the capacitance is lost as the electrolyte freezes. It recovers upon thawing out. I used to work for a radar company and the shipborne units had to work outside in Arctic conditions. There are electrolytics that are made for this but they're physically large and expensive.

Steve A.

Robonz wrote:Hi Andrew, here is the feedback on the PCB as promised and my recommendations if you were to do a respin

Modifications chosen for my build.
8 ) Jumper the powersupply 5V out to the 5V pin on the Arduino

I know it's been a while, but I wanted to comment on the above modification... I have spotted this quote - not specifically for this particular Arduino variant, but nonetheless....

The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board.

So, that's probably why I provided the board with its own 7V via the VCC rather than 5V to the 5V pin.
This modification (supplying 5V to the 5V pin) may be one that is perhaps a bit iffy... ?

I don't do iffy electronics haha. Well at least I think I don't.

This TV/Board has now been powered up for 2 years pretty much non stop now as I get pleasure in demonstrating it to customers that come into my shop.

On another note. When you power the board from USB it feeds 5V to the 5V pin via a mosfet so its doing the same thing. Its just important that it is a regulated 5V,

Robonz wrote:I don't do iffy electronics haha. Well at least I think I don't.

This TV/Board has now been powered up for 2 years pretty much non stop now as I get pleasure in demonstrating it to customers that come into my shop.

On another note. When you power the board from USB it feeds 5V to the 5V pin via a mosfet so its doing the same thing. Its just important that it is a regulated 5V,

All OK then.
Best to clarify/document these things on the forum for those who are to follow
In fact there is someone who is currently building another "ArduinoVisor" so I'm looking forward to seeing that work soon. Fingers crossed!