Software Support > Automated Projects
Setting up Mame / Mala with rotating CRT (Mrotate4)
DaOld Man:
Thats great!
If you are using optoisolators you probably wont need the blocking diodes. The led in the opto is a diode anyway.
Im glad you are getting there.
Some pics would be real nice.
Ropi Jo:
Never really played with optos before so wasn't sure how they would handle the reverse voltage. Already blown up one so don't want to screw up again. But you're right, the LED in the opto should just stay hard off. I'll go for it as-is.
You're also right about the pics... if there's no pics it didn't happen!!
One strange thing I found.... my optos are 6 pin, so the base of the o/p transistor is on a spare pin. When I handle the board I inject 50hz (UK standard) into that pin and the relay turns into a machine gun! I didn't have any 4 pin optos. As long as I didn't touch a certain area of the board with bare skin there was no spurious behaviour so I'll leave it alone.
Ropi Jo:
Read this....
The base connection of the photo-transistor can be left open (unconnected) for maximum sensitivity to the LEDs infra-red light energy or connected to ground via a suitable external high value resistor to control the switching sensitivity making it more stable and resistant to false triggering by external electrical noise or voltage transients.
If I add a 10K to pull the base to ground I wonder how much more current will be required from the switching line?
Have to do a little testing. If I can keep the switching current to just 1 or 2mA with a base resistor added I think that would be good.
DaOld Man:
Did you look up the spec sheet for that opto?
Its probably got a min current on input.
Im not sure what current the comm port is good for, but I would say 5-10 ma should be safe.
I know the old printer port was safely good for around 10 ma.
Ropi Jo:
Connected up the interface in place of the rotate buttons after work today.
Just brilliant! I select a H game in Mala and the screen does it's thing. Same with V. I am really blown away with how this works.
I cant give enough thanks to DaOldMan for all his help with this.
He wrote the programs. Even rewrote mrotate (mrotate4) specifically for my build. Gave me step by step instructions. All in his own time for no reward. Genuinely one of the good guys and there's not many of them left :applaud: :applaud: :applaud:
Got a bit of tidying up to do as it's hooked up with various wires hanging all over the place then I'll get some pics and probably a video or 2 showing some of the moving parts and Mala selecting games.
Got some more control panels to build next and also got to finish getting my roms sorted and loaded.
No rush though. It's onlt taken 6-7yrs to get this far! :cheers:
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