How to use the multimeter??

I've been reading a lot of tutorials on how to use a multimeter, even a very good instructional video. I learn to do things like measuring current, restistance, voltage, etc. Since I want to make fancy custom arcade sticks I need to learn how to do find out things with a multimeter, but I can't figure out how to do it with generic tutorials I've found online.

But I want to do stuff like finding a VCC pin on a controller circuit for a power source to power another LED controller chip, finding a ground pin on a controller PCB and making sure I won't short out my console when plugging in a modified PCB in a controller.

So can anyone find information on how to find a VCC pin on a board, similarly a grounding in and how to check if im not shorting anything out after I've altered it?

 

Finding a ground point on a PCB is the easy one. If you got a known ground point (for example an RF shield, the connection to the power supply ground, a screw holding the PCB to a case, etc), and want to find another one, just do a continuity test between the known ground point and whatever points you want to try. If you got continuity, you've found a ground point.

The best way to find the vcc pin on a chip is simply to get the datasheet for the chip in question, there's as good as always info on the chip's pin configuration in those. To find those datasheets, I usually just google on the chip number, or whatever other identifier I might find, most of the hits will be from datasheet archive sites.

Another way is to start at the power supply and just follow the traces, to get an idea how and where the power is distributed to the different parts/components on the PCB. It might be hard at first, but soon you'll get the hang of it. Or if you know the vcc pin on another component, just do a continuity test between it and the different pins on the chip you want to find it on, when you've got continuity, you've found it. You can also verify it by starting the console or whatever you're working on, and measure the voltage between the leg and ground to see if it matches what you expect it to be.

Also, often power supply and ground traces are broader than signal traces on the PCB, which can be used as a pointer. However this is far from always true.

Basically there are as many ways to do this as there are PCB:s, doing these things is often a question of using your imagination to find a way that works in the particular case


As for shorts, just do a continuity test, if there's no resistance, you've got a short. By the way, a good practice when doing those fiddly solders is to do some continuity tests between the components in the immediate vicinity of where you're gonna solder before doing anything else. When you're done, do the same tests. If everything went correctly, you should get the same result, unless of course you were supposed to either short something or break an existing connection. This also helps when you short legs/solder points/etc by mistake; it's not all that fun to spend hours trying to get it clinically clean from solder to break the connection, just to find that the two points you connected by mistake actually are supposed to be connected, and are so by a trace you didn't see.

Also, it helps tremendeously to learn what some basic components like resistors, capacitors, coils, transistors, diodes, and so on do, how they are expected to behave, and how they are used in a circuit. Once you begin to understand how circuits are built up, everything will slowly start to become clearer

 

It looks like you know how to use a multimeter - it reads continuity, voltage, current, resistance etc. It's not a wonder tool that's going to look at a circuit and tell you how it works. Only decent electronics knowledge will do that.

The things you are trying to do can be done by Googling, usually. You'll find schematics for a lot of controllers online or, as mentioned, pinouts for common chips.

Of course, if you're making them to use with arcade boards, you don't need a fancy circuit - all you need is some buttons! The only time you need a circuit is if you're using an arcade stick on a console. And then, all you do is get a cheap third part controller to sacrifice, open it up, put the circuit board in your stick, then solder wires to the lines you need (i.e. left, right, A, B etc.). Very simple.

 

Thanks guys , I'm asking because I want to make a custom arcade stick for my Saturn. Slagcoin.com is a great resource for doing this and has diagrams on the Saturn controller chips, but ground isn't marked on it.



I've found another diagram by someone else which has ground marked.




I wanted to know if those pins were indeed correct, but with the stuff in this thread it should be easy to figure out now. I just didnt feel right about connecting such a controller with LEDs and everything without a way to check.

 

The Saturn pad is a piece of piss. Anyone should be able to work out where the buttons are! And same goes for ground and +5V - I can see that the huge track is ground (as marked on both) and +5V is marked with a + on the board. Both of those pictures are exactly the same.



Incidentally, I'd use an el cheapo third party pad rather than ruining an official one, personally. Up to you, though!

 

Well the second one has the ground thing marked. I've never done any serious electronic soldering before. The second picture has the ground specifically marked while the first one hadn't. At least a first party has these schematics online, but you're right. The third party controllers are cheaper but there arent schematics for it online, I also don't know how many are common ground. Since the LED controller chip needs those.

Guess I should be reading other tutorials rather then just multimeter ones now. I'll try and look for some PCB tutorials rather then a multimeter tutorial. Thanks for the help.

 

good luck with this, be very cool to see the result.

 

Third party controllers will use common ground too, there's no sense in not doing it for several reasons, the most important ones being that you don't want different grounds with potentially different potentials, no pun intended. And even if there were several independent grounds so to say, you could just ground your led driver to any one of them

Basically, you're just gonna use the PCB, the controller chip, and the cable/connector. I'll have to agree with Retro here, it's a shame to butcher an official pad for this; as you're not gonna use the mechanical components, there's nothing to gain from choosing an official pad over a third party one as donor. The parts that you're gonna use will probably be more or less equivalent quality wise in a third party pad. And with some luck, the controller chip clone in a third party controller is a through hole variant, as opposed to surface mounted, which would make it a lot easier to make a nice little custom PCB instead of using the original one if you want.

And as Retro also mentions, the design is extremely simple. Basically, the chip registers when the different input pins (1-11 and 13) and are pulled down by pressing the corresponding buttons, encodes that to a signal that the Saturn understands, and sends it. A third party pad will most likely be identical electrically. If you can understand how the input works from your pictures, you won't need any schematics for a third party pad either.

 

Thanks for all the help guys and you covninced me, just oredered an el cheapo pad and not a official sega one .

 

Good call. And if you run into problems understanding the circuitry, you can always snap a few pics and post here

 

I got the Superpad 8 for the Saturn. But it has little to no markings on the board and no data sheet available lol. I do need the help of this board. It only has p and then a number for the wires going into the back of the PCB.



Sorry for fuzzy pictures, you dont need to get glasses, my camera just sucks.

There are little electronic plates on front and back for auto fire and slowmotion, I assume that applying a solder bridge between the points in the off position should get rid of those functionalities.


Im going to assume that the black plastic thingy in the middle is the ground, with all the wires going to it. I however dont seem to be able to remove it (with light nail probing) but I don't even know if I should even remove it.

The only markings on it are p's with numbers, the black wire does seem to be p1, how would I confirm whether this is a ground or VCC point?

The numbers for other colors are p2 for purple, p3 for red, p4 for orange, p5 for yellow, p7 for blue, p8 for grey and p9 for white.

Getting to know which side of the pressure plates are ground or signal would be easy enough if I only knew for sure what would be ground and what would be VCC.

Should I just hook the naked PCB up to my saturn and check which of the pins gets me the most current/voltage ? And seeying if i connect a certain side of the pressure plates to a known ground point which side is signal?

 

What type of switch are those auto fire- and slow motion functions using? From the pictures it looks like at least the auto fire switch is a conventional switch that connects the tabs on the PCB to eachother with some kind of little metal thingy? In that case, you're right, just apply a solder bridge reproducing the connection the switch does in the mode you want it to be. However, if it's some kind of switch that there's significant resistance through, it might be a good idea to bridge those with an equivalent resistor instead of just bridging them with a solder blob.

No no, it's not a ground point. The black plastic thingy is epoxy, covering the controller chip. It is possible to uncover the chip, but it's not easy, and you'll most likely end up ripping the copper tracks away from the PCB, or damaging the chip, and there's really no purpose in doing it. Just leave it alone

Here's the pinout of the saturn controller connector: http://www.gamesx.com/controldata/saturn.htm

Just do continuity tests between pin 1 and all the solder points on the PCB in the other end of the cable. When you've got continuity, you've found VCC. Do the same with pin 9, and there you have your ground point.


The buttons are switches that connects a corresponding leg on the chip to either ground or vcc when pushed down. The chip leg connection is the side with a track that runs to the epoxy blob. The other side will be either vcc or ground. My guess is that it is the latter, just like in the official controller, but you can't be 100% sure. However, you really don't need to know that, your replacement switches will work exactly the same either way.

If you want to know anyways, just do a continuity test between the ground point you just figured out and the side of the buttons that doesn't connect to the chip (that is hidden under the epoxy blob). If you got continuity, the buttons connect the leg to ground when pressed, which is registered by the chip, if not, you can assume it works the other way around, and the chip registers a button press when the corresponding leg is pulled up.

You don't have do do anything with the wiring going to the Saturn or the chip itself, you can use those as is. The only thing you need to do is basically to connect switches (eventually in series with resistors to compensate for eventual resistance through the original rubber dome buttons) in parallel with the old switches. If you can get sharper pictures, covering the whole PCB, I'll sketch up how to connect those switches for you directly on the pics.

 

May I post in this thread too? I have a Dualshock PS2 A (Alps) Middle Version, slagcoin says AVOID! AVOID! but why? Is it because of the solder points being too close? And those 3.3 and 7 v points are for stealing power for custom leds, etc., right? And what do I need to do with the point that has the Resistor? I'm assuming that I don't need anything in there.



I hope you guys answer me, people in other forums demotivated me by ignoring my posts

 

It seems like there are other revisions of the Dualshock controller where the switch membrane is connected to the PCB with another type of connector, to which you can connect your new buttons by simply sticking their wires into the holes. In your picture, it's just a bunch of contact tabs printed on the PCB, which you'd have to scrape clean and solder your wires to. The former method is simpler and doesn't demand any permanent modification of the PCB. I can only guess, but this is probably why controller modders prefer those other revisions. The distance between the solder points is definitely not the problem anyways, they're not very close to eachother at all, and even if they were, that's not really an issue.

The 3.3 and 7 v points are the solders for the power lines feeding the controller electronics, but of course you can tap power for additional circuits you want to add to your controller from them too.

I hope I make sense now, English is as you've probably figured out by now not my native language, and this is really hard to explain:

What you're gonna do is basically to reproduce the membrane electrically using conventional switches. From the picture it looks like the little black/grey thingy to the right of the start button on the membrane either is the resistor, or is a connector to connect to a resistor on the PCB. If the resistor is integrated on the membrane, or is connected to the membrane, you will need to have an equivalent resistor in your reproduction of the membrane.

 

Well, I did test it with a screwdriver connecting one point to the common and it produced results, I've been able to navigate the PS2 BIOS menu. But it seems to not work correctly, seeing that it activates my modchip menu everytime the console boots (to call the menu one must hold Triangle plus Circle). I guess it is something to do with the resistor. I'm not really a electronics guy, so if someone could help me with that god damn resistor I'll be grateful. And I thought it would be as simple as "Solder Btn. 1 to point 5, common 8"
Hopefully at least I can solder, a total begginer would not even scrape those contacts, the solder doesn't connect to that copper crap. And I guess that the resistor is built in the PCB, unless little rectangular plastic things can be used for the same purpose.

And by the way, your english is great! Better than my english, that's for sure.

 

Sure, as long as it doesn't stray too far from the original point... might be confusing to answer two different questions in the same thread! ;-)

What do you want to do exactly?

To both of you, if you're just trying to wire arcade buttons, then it's really simple - don't try to over-complicate things.

An arcade joystick is simple. It is just a load of switches.

A console joystick is (usually) more complex. It encodes the data down onto fewer lines, which is decoded in the console.

Both have a similar premise - a switch is pressed which either completes a circuit or changes a voltage level.

Now, look at the above circuits. You'll see the common thing - those squiggly lines where the buttons go. Guess how they work? Yup, they are two contacts, the rubber pad makes contact between the two when pressed.

So all you have to do is "replace" the squiggly bit with your arcade button. Either follow the track back to a solder point on each side, or just scratch a bit of the coating off and solder to the track (carefully!)

 

Thanks for the help! I'll try and do it as simple as possible, if something goes wrong in the process and I can't identify where I missed, I'll make a separated thread. Sorry for the hijacking.

 

Well the main point was figuring out which is VCC or Ground and which side of the copper plates buttons were signal or ground. I'd only need to put signal wires on the signal side and just daisy chain a single wire from all buttons to the ground pin leading into the cable.

That and which is VCC to hook up a LED controller chip to. My main concerns were finding out which pins were what with a multimeter and not short it out. Kaput got me to figure it out, ty. The side of the copper button plate which goes to the controller chip is signal, the wire which goes in with p1 is VCC and the wire with p9 is ground (with the corresponding pin on the other side ofc).

Since the auto fire and slowmotion functions are just 2 plates with a metal bit to connect one or the other, no resistor added, a resistor is not needed.

 

Firstly, ground is by and large the damn great big common connector! ;-)

As mentioned before, if you look up pinouts, they'll usually tell you which pin is ground and which is +5V.

However, you don't need to know which is ground or whatever if you're ONLY hooking up to arcade buttons. A button is a button - there's no polarity!


Usually, you'll hack a controller in one of two ways:

1. Because you want to use a controller (e.g. MegaDrive) on an arcade board.
2. Because you want to use arcade buttons on a console.

For option 1, you just need to take the cable out and wire up a cable to go from the pads to the board.
For option 2, you rip out the circuit board, keeping the cable, then solder buttons onto the pads.

Simple, that! ;-)

*EDIT*

Take the above Saturn pad. Those pictures are dead simple... but if even they are too complex for you, do it the easy way!

1. Look at the pinouts (http://www.gamesx.com/controldata/saturn.htm)
2. Note that the pad is going to be disconnected from the Saturn... NOT live... so you CAN'T damage it!
3. Take your multimeter and put it on continuity.
4. Look at the pinout for the pin you want. Say ground - that's pin 9.
5. Hold one probe to pin 9 on the joystick connector.
6. Probe away on the board! Probe anything - IT WON'T HURT IT! When you get full continuity, you've found your point.

 

I thought I needed to know polarity to hook it up to a LED controller chip though. Since that needs to draw power for the lights it needs the VCC and also needs to be connected to ground in order to have somewhere for the electricity to flow to.

The youtube videos of FGWidgets LED board in action had quite pretty lights.

I thank both kaput and you retro for the advice though. Especially the ground finding bit should help me to check if the pin numbers on my custom PCB are the same as the official Sega numbers (which they prob are).

Will definately posts results here to show how far I got here thanks to both of your help .