Got my first ever Saturn... what mods are worth doing on it?

I recommend you play Croc legend of the gobbos. What an amazingly underrated gem.

 

So it would be better to use a MOSFET instead of a 4011(as per the webpage)? I've checked out the datasheet for the IRF7319 MOSFET and can't see why it wouldn't run off 3.7V. Is there anything which would need to be altered in the schematic? EDIT: I see it may not run under 4.5V. Any idea on any other low power dual MOSFETs which would save me having to use separate P and N channel ones?



I'm currently reading up on MOSFETs because, again, they're not something I'm familiar with. I pretty much understand how to use them to make a latching switch, but as I want to use the start button as my power button as well, I need to find out how to maintain it without automatically switching off the controller when the start button is pressed.

EDIT: Would a Fairchild Semiconductor 9934C be suitable? Would any significant changes need to be made to the circuit above to populate it?

 

With that circuit topology, you have to use complementary MOSFETS - for a latch you need positive feedback, and the P-Channel MOSFET requires negative drive to turn it on - and the easiest way to do that is to use an N-Channel MOSFET (which switches low when there is positive drive on the gate).

That circuit should do what you want - when the output is off, and you press the button it generates a negative pulse (via the 100k R and 1uF C - so the time constant is 100mS) on the gate of the P-channel MOSFET which causes the output to switch high, turning on the low-side N-Channel FET, which then keeps the P-Channel FET turned on.

When you hold the button in, the 10uF C slowly discharges through the 300K R (time constant = 3S) and when the gate drops low enough the both FETs turn off and the load is disconnected.

That Fairchild part has specs for RdsON @2.5V gate voltage, so it looks like it should work with a 3.7V supply.

 

The FS9934C has a dual MOSFET architecture, with both a P-Channel and N-Channel MOSFET, so would the one be enough? It took me quite some time trawling through semiconductor datasheets to find a dual channel one which took less than 4.5V.

I'm starting to understand the circuit above, but the one thing I don't get is the switch marked "Auto-ON/Auto-OFF" - physically, what is it?

Thanks for the help so far, I'd have been pretty lost without it. I may leave it out of the controllers this time round, but will be playing about with the circuit to try and incorporate it in the future.

 

Yes, that device has a pair of FETs, one P-channel and one N-channel, which is exactly what you want for that circuit.

The "auto on / auto off" switch is showing you where you should connect that cap depending on what state you want the switch to come up when the power is applied - if you connect the cap to ground, then it will switch on, if you connect it to the positive supply rail it will switch off.

 

I'm getting round to sticking everything inside the pad and want to have an internal MX1811 charger and use a bi-colour LED with a common anode to use one colour for the power switch and one for the charging circuit, but not sure about hooking it up, as the charging circuit needs a resistor on the LED anode which I'm assuming will effect the brightness of the power switch LED. Should it be fine if I leave the 1.2k resistor from the power switch circuit?

 

Just got round to doing the 50/60Mhz, as my original bicolour LED blew, but I'm really confused as to where I need to solder the Video Mode from the IC. Mmmonkey's guide says it needs to go to leg 79 of IC14, but every other guide I've looked at mentioned jumpers and cutting traces. Also, my board is a VA PAL SD, which I can't find much info on either, apart from this French website which mentions J1 and R29, but I'm still none the wiser as to where I need to solder the IC Video Mode leg to or if anything requires cutting/lifting...

 

x

 

Cool, so I can just solder 5V, gnd and the video mode lead to SW4 and it should work fine?

 

x

 

I just thought about getting voltage for the wireless receivers for my controllers from inside the console instead of using the regulator on my board below. I need 5V for the ATMEL MEGA8s and 1.9-3.6V for the transceivers. 5V comes from the controller ports so is easy and I thought I could just grab 3.3V from the power supply, but whenever I hook it up to my board and turn on the console, the PSU clicks and doesn't deliver the voltage to my board. Can anyone suggest alternative points on the system I could tap in to? I've had a quite Google, but didn't find anything promising.