N64 Rumble Pak battery-less mod diode

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bobrocks95
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N64 Rumble Pak battery-less mod diode

Post by bobrocks95 »

So it's a fairly common mod to make your N64 rumble pak not use batteries and draw 3.3V from the console instead. Supposedly 3+ modded paks will draw too many amps and cause problems, though I don't see anyone having tested that with hard data anywhere.

I want to know about adding a diode in parallel with the motor circuit. This German thread (I see borti in there!) is the only place I see talk of adding a diode to the circuit to prevent flyback/induced voltage going back into the console's 3.3V line. Not a circuit expert but other sources I've found do propose adding a diode for the same reason, so it's at least not a made-up concept. The N64's 3.3V rail definitely doesn't need to be any more unclean than it already is.

In that thread the 2 pictures shown have the diode backwards though... The circuit diagram shows the Cathode (-) end connected to 3.3V, but I'm pretty sure on a 1N4148 diode the Cathode is marked with a black stripe, so they have it connected to what I believe to be the ground pin based on my multimeter check.

So I wired the one 1N4148 I bought in the way I thought it should go (black stripe/Cathode connected to right 3.3V pin), and the rumble became super weak. Either I have it backwards, or maybe its 200mA rating isn't high enough for the circuit, or I bought the wrong thing. (bought this one)

Can anyone offer maybe even just some general engineering advice? I tried to register on the German forum to at least throw an auto-translated question in there, but the registration page wouldn't work for me.
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Syntax
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Re: N64 Rumble Pak battery-less mod diode

Post by Syntax »

You will get a .7v drop using a diode in series soo you might of done that?

The diagram in the thread is correct https://en.wikipedia.org/wiki/Flyback_diode
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bobrocks95
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Re: N64 Rumble Pak battery-less mod diode

Post by bobrocks95 »

Definitely possible, though if it's now getting 3.3V from the console (I did reuse the battery resistor so I'd have to measure the actual voltages), that's 2.6V which should be well within the expected range of what you'd get from two AAA batteries (Panasonic says 0.9 to 1.5V per battery). The rumble was maybe 30% of its original power, nowhere close to what it was without the diode.

Do the pictures in that thread definitely have it backwards? What would the diode do if it was backwards, nothing?
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Smashbro29
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Re: N64 Rumble Pak battery-less mod diode

Post by Smashbro29 »

Could you do 4 rumble paks like this?
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bobrocks95
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Re: N64 Rumble Pak battery-less mod diode

Post by bobrocks95 »

Everywhere I've read said use no more than 2, but like I said nobody could say what kind of amperage it drew or explain the limits of the circuit.
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