Sinclair ZX80 / ZX81 / Z88 Forums

Hi

I found Wilf Rigter's project to build an external connected keyboard like the version from Memotech.

I've found this schematic on this page: http://www.user.dccnet.com/wrigter/inde ... XKBDv3.htm

Unfortunately there is a component in the schematics, that I don't know: "RN1 5.1K". Does anyone have an idea what this part is?

This is my first PCB-project, and I'm trying to create the PCB.
/Martin

mrtinb wrote:Hi

Unfortunately there is a component in the schematics, that I don't know: "RN1 5.1K". Does anyone have an idea what this part is?

Almost certainly Resistor Network!

XorA wrote:Almost certainly Resistor Network!

Is that a component, or just a schematic way to show multiple resistors connected?

/Martin

XorA wrote:Almost certainly Resistor Network!

Ah! I found this component

/Martin

You can use single resistors as well.
The network just save space while one end of resistors are connected all together to allow easy multiple pull down oder pull up resistors in one package.

Hello Martin, welcome to our forum

mrtinb wrote:Unfortunately there is a component in the schematics, that I don't know: "RN1 5.1K". Does anyone have an idea what this part is?

It is a resistor network. This type has six 5.1k ohm resistors, all of which connect one end of each resistor to a common terminal (so this type would have 7 pins). As Pokemon says, they are commonly used for pull-up (to the +V rail) or pull-down (to 0V / GND). Be careful when ordering, as some have individual resistors with no common terminal. Also double check (including testing using a meter on the resistance range) which terminal is common. As putting these in the wrong way round can cause many weird fault symptoms...

If you can't get a 6 way type, a 7, 8 or 9 way type is fine (just ignore the pins you don't need. Or use normal resistors.
If you can't get 5.1k ohm, 4.7k ohm may work.

Good luck

Mark

PS there is a requirement to post up lots of details of your progress, including tech p0rn photos

On the keyboard it would be nice to have keys for cursor that enables both [Shift] combined with [5], [6], [7] and [8].

As the keys have 4 pins one set can be connected to [Shift] and the other to e.g. [5].

Do I need a component that delays e.g. [5] so [Shift] reaches the computer first?

/Martin

Just because switches have four pins does not mean that there are two sets of contacts inside
Most click type PCB mounting switches have four pins for stability.

So check carefully what the supplier says.

Or get a sample (one only) and use a multimeter to test...

See the wikipedia entry to understand all the meanings that tell you how many contacts there are and what type of operation they have.

Mark

Now the PCB design is complete. The board (10 cm x 5 cm) has been ordered in China. It looks quite confusing but this is my first board, and all connections have been made with autoroute.

Now I need to order the ics, sockets, connectors, resistors, diodes and capacitor. Keyboard will be connected with ribbon cable. The 9-pin joystick port will also connected with ribbon cable.

/Martin

I would like to say that all power lines should be much thicker.
kind regards Paul