John's flashing lights!

[the_real_mcp]

Hey John,

Just listening to your latest Podcast... :-)
#28

About your flashing Leds...
Ok, so remember these are effectively diodes, therefore are polarised (like an electrolytic capacitor).
i.e. *must* go in the correct way around.  Google it up.  Often then have a kink (oooerr) or a longer leg to denote the anode (+) connection.
The cathode (short led) shound connect to 0v/ground.  The ground for switches, etc. should be ok, unless there is some mad wiring somewhere?
 
As for Pinball...of course the original lights were bulbs, which can connect any way around as they are not polarised (so basically a resistor).

I am lucky, as I have done electronics since an early age (11), now I am an old feccker at 43! ;-)


Good luck dude,
Cheers,
Dave.

[iankellogg]

He has them in the right way. The issue is ether the LED needs too high of a voltage for the blink signal or it is over loading the circuitry that drives it. I believe he is going to try a different LED bulb that has a lower voltage requirement but if that doesn't work I think it is going to be time for a FET solution.

[iankellogg]

I am listening to the podcast and frustrated listening to it about the blinking LEDs. John, the way those cone buttons work is probably a BJT transistor in there. The reason why you need both +5V and Blink is because +5V is the power and Blink is a signal that turns on and off the BJT. You really shouldn't try to power a LED directly off that blink wire, you are going to overload the PCB circuit that drives that.

[John's Arcade]

I am listening to the podcast and frustrated listening to it about the blinking LEDs. John, the way those cone buttons work is probably a BJT transistor in there. The reason why you need both +5V and Blink is because +5V is the power and Blink is a signal that turns on and off the BJT. You really shouldn't try to power a LED directly off that blink wire, you are going to overload the PCB circuit that drives that.

Oh, really?!?! So I shouldn't try it?!?

[iankellogg]

I am just nervous to do it long term. The buffer chip that is driving the cone button is probably only rated for a few 10's of mA's. When you overload the buffer it is ether protecting it self from too much current or thermally shutting down. While you may be able to get a bright LED to blink directly off the line you could speed up the death of that chip. I actually just got an atari game that has the cone button today so I can figure out how they work this weekend.

[John's Arcade]

Does this make sense?!?!? Some guy on Youtube made it.

http://picpaste.com/tempest_havoc-G7ixzoXO.png


This guy also says this:

"As suggested on the previous video: you want to use only the RED and WHITE wires... not the BLACK!  The logic board cannot drive enough current, but it might be able to sink it.  Also, the RED and WHITE is what the cone button uses, so when the cone button is lit so is the roller.  If you use the BLACK and WHITE then the roller and cone flash the opposite way to each other.  Key message: DON'T USE THE BLACK WIRE AT ALL!"

And, this...

"If the roller LED won't light with just the red and white, then try temporarily removing the white from START 1.  That way, you won't be limited by the START 1 LED's forward voltage.  You can also try flipping the red and white to make sure the polarity is right for the roller LED.  If all this still doesn't work then those 150 ohm resistors are too limiting.  In that case, locate the conversion board, find the common point of the two 150 ohm resistors R30 and R31 (docs are online), and bring a new wire from there to your roller bulb holder, the other side of the bulb holder going to +5v.  Then you'll get full flasher current to your roller bulb (Q18 can sink several amps), and could use either a bulb or a LED of your choice.  BTW, that's what the original Major Havoc does... connects the roller bulb directly to the signal called LIGHT."

[pimppride]

well kind of not what you want to hear but why not move the flashing circuit off the 1p / 2p start buttons and dedicate it back to the roller as the start buttons weren't flashing originally on this game if I interpreted everything correctly...

from there you can work on a mod to get the 1p / 2p flashing...

[iankellogg]

John what he saying makes some sense. Most often things can sink more current than they can supply. You will still need to be careful about  how much current you use though.

[Tighe]

I really think it is best to just use a transistor driven relay. Then you don't run the risk of damage.

A circuit like this is simple and will ensure you don't damage your expensive board.

[iankellogg]

i'm not sure why you would add in a relay to this circuit. the Rds of a nice 10A logic level fet would be fairly comparable to that relay.

[Tighe]

i'm not sure why you would add in a relay to this circuit. the Rds of a nice 10A logic level fet would be fairly comparable to that relay.

The relay isolates the driving voltage, but I agree that it isn't using a lot of current.

[John's Arcade]

I don't know what to do now. I can't make it work. Someone give me some direction!

[iankellogg]

i'm not sure why you would add in a relay to this circuit. the Rds of a nice 10A logic level fet would be fairly comparable to that relay.

The relay isolates the driving voltage, but I agree that it isn't using a lot of current.

Isolates the driving voltage? Driving voltage for the LED? Driving voltage for the LED is going to be +5V or +12V and both of those are well below standard FET voltages. Also I typically don't drive relays with a FET unless the coil is quite large.

[pimppride]

I agree a relay for this seems overkill, I would imagine you should be able to find a diode(s) that could be inserted inline the 5v or 12v path to do a controlled flash, in my experience only time you need to relay is when you need something to carry the load of the operation ( mind you, most all my electrical knowledge I am referring to is 12v electrics in Volkswagen / Porsche restorations  )

[iankellogg]

Relays are cheap and easy to use. FETs take a bit more knowledge. Also Resistance of a relay is usually pretty low (only beat by some fantastic power FETs).

John - I will get something worked up for you this week. It may be crude because I don't feel like waiting 2 weeks for OSHpark.