Any electrical engineers out there?

[Jess Ragan]

http://www94.pair.com/jsoper/gen_2_5200_adap.html

 

Could you guys help me understand these schematics? I've gone over them a billion times and I'm still not sure I understand them.

[Bryan]

http://www94.pair.com/jsoper/gen_2_5200_adap.html

 

Could you guys help me understand these schematics? I've gone over them a billion times and I'm still not sure I understand them.

 

The design uses 2 4052 chips to control the resistance the way a pot would, but with only 3 possible options (left, center, right): 10K, 250K, 500K. Pins 9 and 10 select which resistor is in use, and they're pulled up by 10K resistors to 5V. The controller can pull one of them down at a time. The same circuit is used twice for H and V.

 

You don't get any keyboard support.

[Jess Ragan]

OK, I think I'm starting to get the idea. The integrated circuits act as their own resistors, right? That makes a little more sense... thanks! I'll see what I can do from here.

[Bryan]

OK, I think I'm starting to get the idea. The integrated circuits act as their own resistors, right? That makes a little more sense... thanks! I'll see what I can do from here.

 

Well, the ICs select 1 of 3 resistors. You still need to put the resistors in there.

 

Think of it this way: If you replace a 5200 pots with resistors, then the console will simple think the stick is stuck in one position. The IC acts like an array of relays, connecting the output to only one of several inputs. By putting different resistors on different inputs and changing the select pins, you insert different resistors into the circuit.

[Prodos8]

The IC's are not resistors, the parts list is incomplete. The IC's connect the proper resistor based on the joystick input. I've built three of these and they work great. You need a combination of resistors to get the proper resistance for each position. like the 250kohm you need a 100k ohm and 150k ohm, as they don't make a 250k ohm. For the 500k ohm I used two 1M ohm resistors in parallel, which halves their value. I use mine with a wico y cable to get keypad support. Also if you tie joystick pin 9 to the 5200 upper fire button you'll have two button support with sega pads.

[Jess Ragan]

Man, this stuff is frustrating! Here's a rough schematic of my own that I created, with the circuits color-coded for my own convenience and comprehension. All of the resistors are marked by their ohm values, and none of the circuits connect to each other unless specifically indicated by an arrow. Is this even close to the mark, or will this circuit blow up my 5200 and burn down my house?

Edited August 19, 2007 by Jess Ragan

[Prodos8]

Man, this stuff is frustrating! Here's a rough schematic of my own that I created, with the circuits color-coded for my own convenience and comprehension. All of the resistors are marked by their ohm values, and none of the circuits connect to each other unless specifically indicated by an arrow. Is this even close to the mark, or will this circuit blow up my 5200 and burn down my house?

 

That looks about right to me.

 

You should tie pins 5 & 7 to +5v on the genesis side, the atari controllers use pin 7 for +5v in case you hook one up with an autofire circuit. Also in the instructions, up and down are reversed, it should be up/down not down/up where you hook those pins to the 4052. I discovered that after I built my first one. You'll also need to y off the top row of pins from the 5200 and connect them to a male db15 in order to connect a standard controller for keypad support. BTW use sockets for the chips, that way you don't have to worry about frying them during soldering as they are CMOS.

Edited August 19, 2007 by Prodos8

[Jess Ragan]

All right, I got a couple MORE questions. Is it absolutely necessary to connect power to both 5V pins? My intention was to use a Sega Arcade Pad with this adapter. I know it's heresy to say this on an Atari forum, but I don't like the way the old 2600 joysticks feel, and I didn't have any intention of using a joystick with a rapid-fire switch.

 

Also, do I need to connect power to the standard controller? I'm assuming the answer is yes.

[Prodos8]

All right, I got a couple MORE questions. Is it absolutely necessary to connect power to both 5V pins? My intention was to use a Sega Arcade Pad with this adapter. I know it's heresy to say this on an Atari forum, but I don't like the way the old 2600 joysticks feel, and I didn't have any intention of using a joystick with a rapid-fire switch.

 

Also, do I need to connect power to the standard controller? I'm assuming the answer is yes.

 

No, its not absolutely required. But, it so easy to do why wouldn't you?

 

The standard 5200 crontroller doesn't need +5v, that's why you can't use the cord to make one of these unfortunately.

Edited August 20, 2007 by Prodos8

[Jess Ragan]

All right, all right... please don't do the duh thing. I'm not as experienced with electronics as you and I just want to make sure I'm doing all this right. I do appreciate all the help, though!

[Prodos8]

All right, all right... please don't do the duh thing. I'm not as experienced with electronics as you and I just want to make sure I'm doing all this right. I do appreciate all the help, though!

Sorry for the duh. Not sure how that got in there.

[CPUWIZ]

they don't make a 250k ohm

 

Sure they do, but cheap ones are SMD, through hole ones are like $2.50 a pop.

[Bryan]

The values aren't that critical. I'd buy 470K ohm resistors. Put 2 in parallel for the 250K.

[Jess Ragan]

I was wondering about that, actually. I know some of these adapters have problems with Ms. Pac-Man, Qix, and Vanguard, but I don't think it's just a matter of Ohms... their designs are significantly different from the one I'd like to build. I'll try the 470K Ohm resistors... if they don't do the trick, I can always string 30K Ohms on the end for the full amount of resistance.

[jsoper]

I actually had trouble getting to 500k, the resistor was correct, but the resistance of the other two CD4052 "off" channels was also about that magnitude, so the parallel result was more like 300k or so. My Fluke meter's resistance setting may have been biasing the 4052 slightly different than a 5200 would have though. Finally decided to just trust the 5200's calibration routine, the adapter did work.