standard 100 mils spacing, almost compatible with standard pcb headers, is better if you use the specific tool to "crimp" the wire, not the best electrical contact ( should be tested for power application ), avoid to stress the cable after installation
That's the only solution I knew of (I already have the original tool for assembling it) but, apart from the other problems you mention, it's too high.
As I just wrote, I need to connect several 3 digit displays to several shelves and I wanted the wire to pass below the PCB, without any housing for the LED displays.
I was thinking of placing the TH displays on one side, the SMD electronics on the other side of the PCB and glue a piece of plastic sheet on top of the electronics, which would cover all of the surface except for one strip, where the connector is placed and the wires run.
I will soon be able to show a drawing to better explain the arrangement.
Probaby I should, since I was not planning to put a regulator on each board. But we still have to decide wether to use LCDs or LEDs.
Should it be? I planned to put a rectifier bridge on each board, not only for easing installation, but also because I planned to transmit the few data by reversing the polarity of the power lines.
A 47k resistor connects one of the power lines (before the bridge) to an MCU pin. This is the data input to a SW UART, that will detect the polarity of the space level because that's what it will read during the first 10 seconds after power up.
Fusing is up to you, I guess. The question is: If a single board shorts out, do you want to take down the rest of the system with it? This should happen (if I understand your configuration correctly) since essentially, all the power supplies are in parallel.
My comments about the wire - here in the US, phone cord is typically
24-ga solid copper. That's might small, and easily broken if the cable flexes at all. (stranded would behave better, but 24 ga is still very small.) You'll have to add up all the current paths. The 24-ga nearest your P/ S will be carrying the most current. I suspect (if either LCD or LED), this will still be too much drop, unless you're planning additional voltage regulation at each PCB.
One more thing - not trying to poo-poo the idea, but.... Have you considered EMI/EMC noise abatement? Do you expect the cableing to radiate excessive noise, possibly outside applicable regulatory limits? Twisted cable will help, but you might find you'll need shielded cable
- and if so, that has a direct impact on what kind of connectors you'll want to use. Just my $0.02. I'm not sure I totally understand what you are trying to do...
In the USA, if your clock speed is over 9kHz (which it surely must be??), then you are going to have to pay attention to radiated emissions (intentional or otherwise). FCC Rules Part-2 is a good place to start (47CFR2), then a review of Part-15 Subpart-B (unintentional radiators). Good luck!!
Ok, I will put a bridge made with tiny tiny diodes ;-) Seriously, is that a common failure mode for a MCU handling few milliamps?
Well, if the cable flexes, it means that the shelf flexed, so they will have worse problems to think about.
Ok. The parts James found are able to use up to 18 gauge multistranded, which is 1.35 sq mm, but if I can find one that can host 1.5 sq mm wire, that is our standard "house wiring", that costs some $10 for 100 m, I will use those. Too bad for the twisting...
The line is balanced, so there should not be any variaton of current. I chose an ATtiny48, that has sufficient pins to directly drive trhee
7-segments displays, so I won't need to multiplex them.
I think the clock will be even higher that, but it will be confined inside the MCU. The data transmission rate will be around 16+16 bits * 50 units (out of 150, no average) / 10s = 500 bits per second.
Maybe much less, since I will probably opt for more than one power supply/transmitter. 1A stuff is much cheaper and available than 5A, and some redundancy does not hurt.
Thanks, but here we use, for this kind of equipment, EN 60945 (emission) and EN 61000 (susceptibility), and I'm proud to say that every time I went to the anechoic room, my stuff always passed the tests "at first sight" with no modifications whatsoever.
Every cent is treasured. I'm trying to ease the job of people that distributes magazines and newspapers. A PC knows how many copies of which papers go to each kiosk, lights and flashes the relevant displays, an operator collects the displayed number of copies, resets the display and brings the trolley to a checkout counter.