# Help hook up a Vectrex controller to a PC

T

#### [email protected]

Jan 1, 1970
0
Okay, so I'm writing an article about how to play classic vector arcade
games on your Vectrex. I've got it all working nice, but I'd like to
create an interface to use the original Vectrex contoller. Here's what I
know.

The original controller varies the voltage on the X/Y output pins from -
5v to +5 volts as you move the stick. The interface I'm using to the PC
is an A-Pac from Ultimarc.

http://www.ultimarc.com/a-pac.html

It measures the resistance across 5k, 10k, 50k or 100k pots for its XY
inputs.

I'm pretty clueless as to how to go about translating the output from
the Vectrex controller to a varying resistance in the range required.
The other problem is that I won't have a -5v source, only the +5v
present on the a-pac.

TIA,
Tim

J

#### Jasen Betts

Jan 1, 1970
0
Okay, so I'm writing an article about how to play classic vector arcade
games on your Vectrex. I've got it all working nice, but I'd like to
create an interface to use the original Vectrex contoller. Here's what I
know.

The original controller varies the voltage on the X/Y output pins from -
5v to +5 volts as you move the stick. The interface I'm using to the PC
is an A-Pac from Ultimarc.

http://www.ultimarc.com/a-pac.html

It measures the resistance across 5k, 10k, 50k or 100k pots for its XY
inputs.

I'm pretty clueless as to how to go about translating the output from
the Vectrex controller to a varying resistance in the range required.
The other problem is that I won't have a -5v source, only the +5v
present on the a-pac.

what's inside the vectrex controller, is there's nothing but a pair of
potentiometers you can probably connect it directly to a PCs joystick
port.

Bye.
Jasen

T

#### [email protected]

Jan 1, 1970
0
In said:
what's inside the vectrex controller, is there's nothing but a pair of
potentiometers you can probably connect it directly to a PCs joystick
port.

Bye.
Jasen

I'd like to accomplish the objective without opening the controller. You
have to ruin the stickers to open them.

If I use a volt meter to test the resistance on the X pin to ground, it
goes like this as I move the stick from far left to far right: 20k ->
10k -> 20k. Far left has the exact same resistance as far right. That
won't work. I need to know if there is a way to convert voltage to
resistance; whether that's against the laws of physics or just economics.

Tim

P

#### petrus bitbyter

Jan 1, 1970
0
I'd like to accomplish the objective without opening the controller. You
have to ruin the stickers to open them.

If I use a volt meter to test the resistance on the X pin to ground, it
goes like this as I move the stick from far left to far right: 20k ->
10k -> 20k. Far left has the exact same resistance as far right. That
won't work. I need to know if there is a way to convert voltage to
resistance; whether that's against the laws of physics or just economics.

Tim

Tim,

Economics I guess. You can control a servo system (motor + controller) with
a voltage and you can drive a pot with a servomotor. Servos for hobby use
are available. They're used in model aircraft for instance. So technically
the problem can be solved but I bet it's not cheap.

Can't you find out how a-pac reads out the pots? Maybe you can fake the
a-pac once you know.

petrus bitbyter

J

#### Jasen Betts

Jan 1, 1970
0
I'd like to accomplish the objective without opening the controller. You
have to ruin the stickers to open them.
If I use a volt meter to test the resistance on the X pin to ground, it
goes like this as I move the stick from far left to far right: 20k ->
10k -> 20k. Far left has the exact same resistance as far right. That
won't work. I need to know if there is a way to convert voltage to
resistance; whether that's against the laws of physics or just economics.

what about measuring from the +5 and -5 terminal?

Bye.
Jasen

T

#### [email protected]

Jan 1, 1970
0
In said:
what about measuring from the +5 and -5 terminal?

Bye.
Jasen

Ah ha! Yes, that makes it more clear. What happens is this:

When you move the stick left, resistance between -5v and X is 0k. Resistance between X and +5v is 10k.

When you center the stick, resistance between -5v and X is 20k. Resistance between X and +5v is 20k.

When you move the stick right, resistance between -5v and x is 10k. Resistance between X and +5v is 0k.

This makes complete sense if it's going to vary the voltage between -5 and +5, with 0v being center.

Now... is there a relatively simple way to convert that to instead provide a range from 0k to 20k as I move the stick from left to right, with 10k being in the center... without opening the case?

Overview of desired conversion

Current Behavior / Desired behavior

Left / Left
-5 to X = 0k A to B = 0k
+5 to X = 10k

Center Center
-5 to X = 20k A to B = 10k
+5 to X = 20k

Right Right
-5 to X = 10k A to B = 20k
+5 to X = 0k

I think it's above my skill level to figure out a simple cheap way to do it.

Thanks,
Tim

J

#### Jasen Betts

Jan 1, 1970
0
Ah ha! Yes, that makes it more clear. What happens is this:

When you move the stick left, resistance between -5v and X is 0k. Resistance between X and +5v is 10k.

When you center the stick, resistance between -5v and X is 20k. Resistance between X and +5v is 20k.

When you move the stick right, resistance between -5v and x is 10k. Resistance between X and +5v is 0k.

This makes complete sense if it's going to vary the voltage between -5 and +5, with 0v being center.

Now... is there a relatively simple way to convert that to instead provide a range from 0k to 20k as I move the stick from left to right, with 10k being in the center... without opening the case?

Overview of desired conversion

Current Behavior / Desired behavior

Left / Left
-5 to X = 0k A to B = 0k
+5 to X = 10k

Center Center
-5 to X = 20k A to B = 10k
+5 to X = 20k

Right Right
-5 to X = 10k A to B = 20k
+5 to X = 0k

hmm X - +5 X - 0V x - -5

Left 0 20K 10K
centre 20K 0 20K
right 10K 20K 0

that's a puzzle in itself hmmm...

+---------------------- X
|
V
(+5)-[35K]-(0V)-[35K]-(-5)
| |
--------[11K7]--------'

that would produce what you measured... hmmm no. there's a Y also

-------+---------------------- X
|
V
(+5)-+-[70K]-(0V)-[70K]--+-(-5)
| |
+-------[11K7]------'
| |
-[70K]-(0V)-[70K]--'
^
|
----------------+------------- Y

I wonder why they did ty like that...

anyway the best way to use it looks to be as a voltage divider

I think it's above my skill level to figure out a simple cheap way to do it.

it's taxing me too.

joystick inputs don't need to be driven by variable resistors to +5V
anything that can cause the internal 555 chip (equivalent) to change state
at the right time will do, you could use a variable current source. but
to get a linear response you'd need to vary the current as the reciprocal
of the input voltage.

iK typ
? ---> >---/\/\--+-DIS
+-THR
+-TRI
|
===
| 10n typ
0V

hmm is there a way to do 1/X using op-amps?

Bye.
Jasen

T

#### [email protected]

Jan 1, 1970
0
In said:
I wonder why they did ty like that...

anyway the best way to use it looks to be as a voltage divider

it's taxing me too.

I found the actual schematic of what's inside there.

http://www.o-sd.com/misc/vecman-21.jpg

The pots are 10k.

I still haven't figured out how to do it.

Tim

J

#### Jasen Betts

Jan 1, 1970
0
I found the actual schematic of what's inside there.

http://www.o-sd.com/misc/vecman-21.jpg

The pots are 10k.

I still haven't figured out how to do it.

get a busted one and replace the pots.

I made a joystick once, got two pots tied the spindles together
at 90 degrees, attached one pot to a bracket on the base
and the other to he stick.

It did the job, (got me through galactix)

there's a way - I think you'll need either exponential and log amplifiers
stages or a pwm stage, I don't think the correct transformation can be done
using only linear combinations.

I think It's beyond me.

Bye.
Jasen

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