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Is it possible to insert a power LED into the SMS2?

I am currently putting the reset switch in and looking at making a SMS reader too!. I love this site, its full of usefull stuff, I just wonndered if its possible to input a power LED, I know absolutley nothing about pins and powers etc, I just play about.

Thanks for a gre at si te

Yes, of course it's possible, both my SMS II consoles from Tec Toy have Power LED and Reset Switch....
There's my trick on how i found that:
Locate the 7805 Power regulator in your board, it's like a HUGE transistor, and have just three pins onto it, it's on most left-hand on the board, and maybe have the system ground screwed onto it...
You'll have to use pin 2 to ground, and pin 3 to power on (+5VCC)....
That's so easy doing....
About the reset button, another easy one mod, you just have to solder a 2 pin button, using one pin in the mapper chip of the console (that one just like in the cartridges one), and another in ground (you can use the same from 7805 or even the RF shielding)...
look a way the chip is:

pin one
-------------
)
-------------
you'll have to solder in the oposite pin of pin one..., the pin on the most right-down in the board...
Be careful because in some boards the chip is soldered reverse okay?
Be careful too because some versions of the SMS2 board from tec toy DOESN'T have the mapper chip, and i don't know how to mod using those boards...
Hope this helps you ;-)

Thanks for your help, I am using the Pin 33 on 315-5237 to 0V method for the reset which I am finding it slightly hard to solder onto pin33 but I thin this is due to me having rubbish solder.

I also would like to do the 50/60Hz switch and I think I know what I am doing.

Thank's for the LED help, first try (without soldering) I put the LED accross pin 1 and 3 which blew the LED that was a new experiane as I have never made an LED pop. Fingered it out tho, thanks for the help and again, this is a

g r e a t s i t e !

P.S.
How much would you be able to sell a modded SMS2 for? Either Ebay or local game shop. Because I am modding my spare but I am thinking about selling it as they can fetch around £30 inc 2 pads and 2 games around my area. A mega drive with CD drive is about £50! But I have never seen a SMS1! I really enjoy playing on my old consoles and I love people taking the mick when I buy my 99p game for them!

Well, a tip for soldering in that chip is you pick up a smal bit of blu-tack, or insulating tape, and glue the wire there, then you press down the wire with a screwdriver, the wire will be on place there and so much easier to solder!
Well, the PAL/NTSC mod works as well, but you shoudn't try that because if you got difficulties soldering that simple wire, it will be a very risk of screwing up your sms video processor...
well, the led will blow up for sure if you put into the 1 and 3 pins, because there will be a difference of more than 11 volts between those pins, and the led usually takes 5 volts

You need a limiting resistor in series with the LED. It's value depends on the LED's specs. http://led.linear1.org/1led.wiz

For a 9volt source I think I used a 75 Ohm resistor, its just something to restrict the flow so you don't stuff up the led. Better yet connect it to a variable pot then you can increase and decrease the brightness of the led as you see fit (Actually thats a stupid idea but anyway).

Jacko and albino_vulpix, a resistor is not necessary putting to limit voltage in that case, because in the output of 7805 will be 5 volts, exactly what the led's take...
But why the led blew up in that case?
if you put into pin one to pin three, will be a differential voltage up to 11 V depending on the system...
if you solder to pin 2, which is ground, and pin 3 , which is the output, will work normally, i have 2 SMS2 systems with this mod for a long time, and none had blew a single led...

You need resistors inline with LEDs because they have a low resistance and thus can easily take more amps than they're rated for and burn out too fast.

Rony if you follow albino's reference to the led site you'll find an article entitled "The myth of the 5V LED". LEDs typically have a forward voltage drop of 2V and most standard LEDs operate optimaly at around 20mA. Hence the current limiting resistor is required to prevent the LED from burning out. A typical value for this limiting resistor is around 220 ohms.

Note: There are some LEDs available with built in current limiting resistors but they are less common and more expensive.

If you want a fancy blue LED they typically have a forward voltage drop of around 3.3V and operate up to 30mA.

For the technically minded the formula is:

R = (Vs -Vf) / If

Where:
R is the limiting resistor's value in ohms
Vs is the supply voltage (5 volts in our case)
Vf is the forward voltage drop of the LED (see LED data sheet)
If is the recommended forward operating current of the LED (see LED data sheet)

Whatever value you calculate for the resistor round it up to the nearest standard E12 or E24 series resistor.

Pushing a LED beyond it's rated specification will shorten its working life. Again RTFM (Read The Flaming Manual [data sheet])!

As for putting a reset button on an SMS2, you need to take care. Pin 33 on the 315-5237 ASIC is indeed the reset button input pin, however, it is tied to VCC (+5V) on my PAL SMS2 board (IC BD M4Jr. PAL SEGA 171-5922A). So pulling it to ground will actually short out the power supply. This will definately give you a reset of sorts.

The 7805 (5V linear voltage regulator) does have some short circuit protection but repeatedly abusing it in this manner is not likely to do it any favours.

Regards
Marty

Well, i didn't know about that anyway, thanks for the advice ;-), but it's already another difference, my SMS is manufactured by Tec Toy, and atlhough it's a SMS2, it have a 315-5016 mapper chip inside, and the reset is really logical, because if i made the "Infinite Lives" cheat in Black Belt, it works as well, and the game "The Smurfs" doesn't restart pressing reset...
Well, i said that i put a LED, yes, i put onto the Sonic SMS2 i have, but i have one with Alex Kidd built-in, that isn't a led inside, it's a 6V miniature light bulb, but it does work as well :-)
I'll try fitting a resistor between the 7805 and the led, because i doesn't want to see it burning, but i'm using it from 3 months + and no flaws since then...

Author	Message
30021190 Joined: 11 Jun 2007 Posts: 6	SMS2 Power LED Posted: Mon Jun 11, 2007 9:52 pm
30021190 Joined: 11 Jun 2007 Posts: 6	Is it possible to insert a power LED into the SMS2? I am currently putting the reset switch in and looking at making a SMS reader too!. I love this site, its full of usefull stuff, I just wonndered if its possible to input a power LED, I know absolutley nothing about pins and powers etc, I just play about. Thanks for a gre at si te

Rony_ket Joined: 09 May 2007 Posts: 137 Location: Sampa, Brazil	Posted: Mon Jun 11, 2007 11:11 pm
	Yes, of course it's possible, both my SMS II consoles from Tec Toy have Power LED and Reset Switch.... There's my trick on how i found that: Locate the 7805 Power regulator in your board, it's like a HUGE transistor, and have just three pins onto it, it's on most left-hand on the board, and maybe have the system ground screwed onto it... You'll have to use pin 2 to ground, and pin 3 to power on (+5VCC).... That's so easy doing.... About the reset button, another easy one mod, you just have to solder a 2 pin button, using one pin in the mapper chip of the console (that one just like in the cartridges one), and another in ground (you can use the same from 7805 or even the RF shielding)... look a way the chip is: pin one ------------- ) ------------- you'll have to solder in the oposite pin of pin one..., the pin on the most right-down in the board... Be careful because in some boards the chip is soldered reverse okay? Be careful too because some versions of the SMS2 board from tec toy DOESN'T have the mapper chip, and i don't know how to mod using those boards... Hope this helps you ;-)

30021190 Joined: 11 Jun 2007 Posts: 6	Posted: Mon Jun 11, 2007 11:40 pm
30021190 Joined: 11 Jun 2007 Posts: 6	Thanks for your help, I am using the Pin 33 on 315-5237 to 0V method for the reset which I am finding it slightly hard to solder onto pin33 but I thin this is due to me having rubbish solder. I also would like to do the 50/60Hz switch and I think I know what I am doing. Thank's for the LED help, first try (without soldering) I put the LED accross pin 1 and 3 which blew the LED that was a new experiane as I have never made an LED pop. Fingered it out tho, thanks for the help and again, this is a g r e a t s i t e ! P.S. How much would you be able to sell a modded SMS2 for? Either Ebay or local game shop. Because I am modding my spare but I am thinking about selling it as they can fetch around £30 inc 2 pads and 2 games around my area. A mega drive with CD drive is about £50! But I have never seen a SMS1! I really enjoy playing on my old consoles and I love people taking the mick when I buy my 99p game for them!

Rony_ket Joined: 09 May 2007 Posts: 137 Location: Sampa, Brazil	Posted: Tue Jun 12, 2007 1:03 am
	Well, a tip for soldering in that chip is you pick up a smal bit of blu-tack, or insulating tape, and glue the wire there, then you press down the wire with a screwdriver, the wire will be on place there and so much easier to solder! Well, the PAL/NTSC mod works as well, but you shoudn't try that because if you got difficulties soldering that simple wire, it will be a very risk of screwing up your sms video processor... well, the led will blow up for sure if you put into the 1 and 3 pins, because there will be a difference of more than 11 volts between those pins, and the led usually takes 5 volts

albino_vulpix Joined: 05 Jun 2007 Posts: 258 Location: Melbourne, Australia	Posted: Tue Jun 12, 2007 6:17 am
	You need a limiting resistor in series with the LED. It's value depends on the LED's specs. http://led.linear1.org/1led.wiz

Jacko Joined: 01 Feb 2004 Posts: 1464 Location: Sunny ol Tamworth, New England NSW AU	Posted: Tue Jun 12, 2007 6:43 am
	For a 9volt source I think I used a 75 Ohm resistor, its just something to restrict the flow so you don't stuff up the led. Better yet connect it to a variable pot then you can increase and decrease the brightness of the led as you see fit (Actually thats a stupid idea but anyway).

Rony_ket Joined: 09 May 2007 Posts: 137 Location: Sampa, Brazil	Posted: Tue Jun 12, 2007 9:08 pm
	Jacko and albino_vulpix, a resistor is not necessary putting to limit voltage in that case, because in the output of 7805 will be 5 volts, exactly what the led's take... But why the led blew up in that case? if you put into pin one to pin three, will be a differential voltage up to 11 V depending on the system... if you solder to pin 2, which is ground, and pin 3 , which is the output, will work normally, i have 2 SMS2 systems with this mod for a long time, and none had blew a single led...

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14769 Location: London	Posted: Tue Jun 12, 2007 10:19 pm
	You need resistors inline with LEDs because they have a low resistance and thus can easily take more amps than they're rated for and burn out too fast.

Marty Joined: 19 Dec 2005 Posts: 34 Location: United Kingdom	Posted: Sat Jun 16, 2007 4:08 pm
	Rony if you follow albino's reference to the led site you'll find an article entitled "The myth of the 5V LED". LEDs typically have a forward voltage drop of 2V and most standard LEDs operate optimaly at around 20mA. Hence the current limiting resistor is required to prevent the LED from burning out. A typical value for this limiting resistor is around 220 ohms. Note: There are some LEDs available with built in current limiting resistors but they are less common and more expensive. If you want a fancy blue LED they typically have a forward voltage drop of around 3.3V and operate up to 30mA. For the technically minded the formula is: R = (Vs -Vf) / If Where: R is the limiting resistor's value in ohms Vs is the supply voltage (5 volts in our case) Vf is the forward voltage drop of the LED (see LED data sheet) If is the recommended forward operating current of the LED (see LED data sheet) Whatever value you calculate for the resistor round it up to the nearest standard E12 or E24 series resistor. Pushing a LED beyond it's rated specification will shorten its working life. Again RTFM (Read The Flaming Manual [data sheet])! As for putting a reset button on an SMS2, you need to take care. Pin 33 on the 315-5237 ASIC is indeed the reset button input pin, however, it is tied to VCC (+5V) on my PAL SMS2 board (IC BD M4Jr. PAL SEGA 171-5922A). So pulling it to ground will actually short out the power supply. This will definately give you a reset of sorts. The 7805 (5V linear voltage regulator) does have some short circuit protection but repeatedly abusing it in this manner is not likely to do it any favours. Regards Marty

Rony_ket Joined: 09 May 2007 Posts: 137 Location: Sampa, Brazil	Posted: Sat Jun 16, 2007 4:29 pm
	Well, i didn't know about that anyway, thanks for the advice ;-), but it's already another difference, my SMS is manufactured by Tec Toy, and atlhough it's a SMS2, it have a 315-5016 mapper chip inside, and the reset is really logical, because if i made the "Infinite Lives" cheat in Black Belt, it works as well, and the game "The Smurfs" doesn't restart pressing reset... Well, i said that i put a LED, yes, i put onto the Sonic SMS2 i have, but i have one with Alex Kidd built-in, that isn't a led inside, it's a 6V miniature light bulb, but it does work as well :-) I'll try fitting a resistor between the 7805 and the led, because i doesn't want to see it burning, but i'm using it from 3 months + and no flaws since then...

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