Interconnect PCB options, please?

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Professor601

New Member
Greetings, programs.

I am working on the next rev of my current Picaxe project, which is going to need to fit into a small space (1" {2.5 cm} diameter pipe). I wish to connect a smaller I/O board that will have a few LEDs and three sensors on it to the main PCB I will design that will hold a Picaxe, an Op Amp, and a few other odds and sods. The assembly idea I have right now will entail attaching the I/O board into the case, then conecting the main board using some sort of standard connector system before I slide it in and secure it to the case. Right now I expect I will need a minimum of 10 wires in the connection.

So, advice please: there are gazonkers of different kinds of connectors out there. What might members of this esteemed fourm suggest I look for? I expect it will need to be wired rather than a M/F header connection, but any thoughts on how to narrow down my search? I'm a tad overwhelmed by what Mouser has to offer.

Courteously,
The Professor (601)
 
techElder

techElder

Well-known member
Hey, professor. I'm not a "program", but I have a suggestion ... go serial ... add more PICAXE processors.

Why do you have a connection point, anyway? Can you put everything on one long board and minimize the connections?

What kind of signals etc. are on those 10 wires?

How tight does it get inside of that 1" pipe? Does anything have to move or slide?
 
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Professor601

New Member
Space is my issue right now. I am hoping to have a pocketable device. My current version works well enough but is nearly 22 cm long, so it is not quite as portable as I hoped. Once the boards are installed nothing else has to move internally. Data through the wires will be some on/off voltage to LEDs, a variable voltage from a UV sensor (~1-3 volts) and two weaker signals, one from a thermopile and one from a Hall Effect sensor, plus Vcc and ground.

I'm not quite certain what you mean by 'go serial', in that I don't see how adding a Picaxe would help me along here, but I will entertain any education for this and future projects. And surely someone must remember Tron?

Courteously,
The Professor (601)
 
techElder

techElder

Well-known member
Ah, Tron! I always wished for a motorcycle with infinite traction!

At least Tron was visual. So far, your project is only titillating mental pictures in my mind. Schematic would be adventurous, but necessary.

"Serial" means to process data and send the processed data through a common interface of only two wires instead of 10.

Having only a flicker of description of your project is not enough to describe further solutions.
 
hippy

hippy

Ex-Staff (retired)
Professor601 said:
I'm a tad overwhelmed by what Mouser has to offer.
Click to expand...
I am not sure anyone would really be any better placed than yourself to decide which to use, without further details of acceptable and unacceptable criteria. Something cheap, second-sourced, commonly available, available in the quantities ( high or low ) you wish to purchase, I would guess were the basic criteria.

You could possibly use 0.1" header pins and IDC ribbon cable links as those are fairly common and can easily be home assembled, should fit the tube dimensions.

Or just solder flying wires to the first insert, solder those to the other board once fitted.

Just using a single board as Texasclodhopper suggests is the easy course and worth considering, at least costing out as separate and combined boards.
 
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Professor601

New Member
Thank you for the explanation of serial in this context. I had not considered that, even though of course I knew the Picaxe chips could do that kind of communication.

More directly, were I to the schematic point yet, I would glad post one. This is sort of "what if" phase of the project where I want to think through what I might be able to do, but to perhaps put some flesh on the bones: I have developed something I am calling a spectral screwdriver (yes, nod to Doctor Who) that can emit and scan for a variety of light and energy. My current working version can scan for temperatures using a thermopile, get a UV reading for an area (eventually calibrated to a UV index) and locate bright source of UV light, and detect magnetic fields down to around 75 gauss (strong refrigerator magnet) as well as emitting light through an RGB LED, a 395nm UV LED and IR at 950nm (mostly to use as a simple remote, eventually).

I learned a lot about how to make it work in my current version, but I want to make a better, and slightly smaller version. As my manufacturing capability are somewhat limited, having a smaller board to fit these sensing components and LEDs onto that I could more easily match openings to is my main thought, hence the original question. But I always take a lot to think about from these forums, so thanks again for all the input.

Courteously,
The Professor (601)
 
techElder

techElder

Well-known member
Perfesser, this sounds like a good application for an i2c buss. You could use small USB-style connectors for i2c, because there will have to be 4 wires: VCC, GND, CLK and DATA.

Normalize your sensors to be read by ADC, etc. at the sensor location. Use, for example, a 20X2 as an i2c slave at each sensor.

All the slaves are connected to the same i2c and have individual addresses.

A master i2c device queries each i2c slave as needed and handles the processing. The master could write compensation values, etc. back to any slave, so you could tweek the output.

Could still be very small (eventually) with surface mount devices.
 
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