I2C relay boards.

PCF8574-I2C-Bidirectional-I-O-Expander-Relay-Control-SmartHome-Ardiuno-Raspberry

Used with:

/8-Eight-Channel-5V-Relay-Module-Board-with-Optocoupler-Power-Supply-PIC-ARM

gives you eight relays for $9.29 plus some wires between the modules.

Seen many versions of that. Want an integrated board w/relays. Found several but all thus far are international $hipping.

OK, make your own. A schematic of that board is online.

I don't follow what is so bad about international shipping? The typical vendor of inexpensive boards is in Asia and ships for free. I found two on eBay that sell 8 channel I2C relay boards with a different form factor for $80 or $90 in the US. Where are you?

Worst option. Avoiding manufacturing anything; just exponential time-sink. Would prefer the integrated board but may end up with split approach.

-- A host is a host from coast to snipped-for-privacy@nrk.com & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433

The split configuration would make it easier to repair, and the control boards can be plugged end to end. You can eliminate the jumpers on the headers with a drop of solder on the underside of the boards.

If a relay board or controller board fails, it will be much cheaper to repair. You can buy ready made 40 conductor cables with single Dupont contacts on Ebay to harness them together. I remove the single contact shells and replace them with a single, with the proper number of positions. That way, my projects look a lot neater than the typical wad of individual wires.

I may use a pair of these boards in a custom, multiple iron soldering station that I'm building.

The best boards we've found are: as they come with 24V relays, an advantage.

But price it out:

$35 board, $31 of shipping.

And form factor does matter to us.

I need some 10 position one-row headers but will likely use two-row 20's and ignore the other. I do plan to plug them end to end but will need to hold them. Thinking a slotted /______\ piece of soft plastic that in turn is mounted to the DIN rail.

Yes, ribbon cable. Peel off as many conductors as you need. The color code repeats every ten conductors.

T1-3X-40pcs-20cm-Male-To-Male-Female-Dupont-Wire-Jumper-Cable-Arduino-Breadboard

I'd rather use an IDC connector that matches the headers; less chance something gets loose/ is misconnected.

The IDC connector is a solid block and fixed size. The "Dupont" cables can be used in any width or as individual wires. The connectors on the end aren't tied on with string. They work great. You can get them in either male or female on both ends and in any combination. Very flexible indeed.

Yes, I see. But they are fixed length. With ribbon+IDC, I can make the cables the correct length.

They are available in many lengths, mostly multiples of 5 cm. Works for me.

Really? Have you ever used the Dupont connectors? They are reliable, and inexpensive.

I've used thousands of them, along with IDC. Only a keyed header and a keyed IDC connector will prevent misconnecting a cable. The color coded wire that I mentioned makes it easy, since they follow the standard color code. Start with black for pin one. Consider it the stripe on typical ribbon cable.

Shouldn't black be pin zero?

If you can find a pin zero, you can use it.