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Um'ing and Ar'ing

A project log for Retro rack and backplane computer

Old style modular system for development of retro computers

Hacker404Hacker404 03/21/2017 at 07:520 Comments

Connector - what to choose?

I was trying to decide between an 80 pin header (top left) or a 50 pin IDC style socket (top right).

And a SMT (header bottom left) or a through-hole header (bottom right).

It seems that the options are not as diverse as I expected.

Old 5 Volt chips need a bit of current to heat up their micro-steem-engines. lol

So I was wondering how many pins to connect together for the power feed. To that end I started pulling things apart and here is what I found -

The contact surface area of the through-hole header is minuscule. The SMT header has about 6 to 8 times the contact surface area.

I really didn't want to use a SMT header because I worry about the connector lifting out of the solder.

So the problem now is - If I use the through-hole header then the 50 pin connector is not enough because I will need to use at least 4 pins for 5 Volts and 4 pins for ground. Perhaps I could just use a larger connector like 76 pins?

Even with the SMT header, I would probably use 2 pins for GND and 2 pins for 5Volts and I also wanted a 12Volt rail, so another to pins and thay makes 6. The Z80 CPU has 38 signal lined + 6 pins for power is 44pins so it only leaves 6 pins free in a 50 pin connector.

So I am going to do one of two things -

1) Just start with DIN 41612 like someone mentioned in the comments as they are rated at 2 Amps per pin - or use something different to start with and upgrade to the DIN later.

2) Make the layout so that it can be upgraded to DIN 64 pins (two rows A/c). I might put extra pins on either end for the power when using the cheaper connectors and just ignore them for DIN.

There are also other problems with the cheap connectors. They are not self-aligning like DIN so there will be some jiggling to get them in.

Option 2 above sounds good as it gives me the opportunity to find out how bad the cheap connectors are and recover by replacing them with DIN except ... I will be using cheap SMT connectors and the DIN are through-hole.

I am sending an order off in the next couple of days so I will see what I end up getting.

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