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BS2: Vdd, Vin, P0-P15 - Voltage, mA ? — Parallax Forums

BS2: Vdd, Vin, P0-P15 - Voltage, mA ?

IceFireProIceFirePro Posts: 86
edited 2010-06-17 14:23 in BASIC Stamp
Hi!

I know that each of the P0 to P15 input/output pins is capable of delivering up to 20mA of electricity at 5 volts regulated.

Question:

I know that Vin delivers as much as the power source connected to BS2 does - but how many mA can it supply?

What about Vdd - It delivers 5 volts regulated, but does it support more than 20 mA?

What's the overall mA the PIC can deliver thru P0-P15 altogether?

Thanks!

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-06-17 04:03
    1) Vin doesn't "deliver" current. It's the input for the voltage regulator on the Stamp module.

    2) Vdd is either the output of the regulator (if you're supplying power to Vin) or the input to the rest of the Stamp module of +5V. To find out how much current the regulator can supply, look at the schematic of the Stamp module and note the part number of the regulator, then get the datasheet for the regulator which will tell you how much current it can supply. Another factor is power dissipation. There's no heatsink for the regulator and it will shut itself down if its temperature gets too high (see the datasheet for exactly what that means). The power dissipation is (Vin - 5V) x Current_Drain.

    3) Read the datasheet for the microprocessor used by the Stamp. The BS2 uses a PIC and the other BS2 models use an SX. The datasheets give absolute maximum current for the I/O pins. Sometimes there's a maximum for each group of 8 I/O pins and for the whole PIC/SX.
  • IceFireProIceFirePro Posts: 86
    edited 2010-06-17 04:42
    But wait, on my BS2, on top, between Vdd and Vss, I have three pins marked "Vin". How come they don't deliver electricity? (That's where the servo goes)?

    So, I'm still looking for a basic example of how to create a 6V flashlight turn on and off through P0 on BS2...
  • IroneIrone Posts: 116
    edited 2010-06-17 07:47
    How Ya Doin'? Are you going to power this flashlight with the battery for your stamp? Does it have an incandescent lamp? They take a lot more amps than a LED. They shove so much electricity into them that they get white hot!!! Two "D" cells will last for a couple of hours if you leave it on and you can feel the heat with your hands. I do not believe it would do your regulator much good. You could use a transistor to power it from around a 1000 ohm base resistor from PO and·with a resistor for excess voltage ( Ohm's Law ) but you must also take into the fact of the watts needed so you do not burn up an 1/8 watt resistor with too much power.·The BS2 has a lot of power for a PIC but·they are only there to be the boss, not do the dirty work.

    Casey

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I fish, therefore I lie!
  • Mike GreenMike Green Posts: 23,101
    edited 2010-06-17 14:23
    The "headers" (that's what they're called) on the board are labelled "Vin", "Vdd", and "Vss". As is usually the convention, these are connected to the Stamp pins of the same names. "Vin" is also connected to the power supply connector. If you have a battery or AC power supply connected to the power supply connector, you should see that connected to "Vin" (and its ground connected to "Vss").

    Regarding the "flashlight" example ...

    First you have to decide what kind of flashlight you want, how much voltage and current the light source requires to operate properly. Then you have to decide whether the Stamp can provide that directly. If not, there are different choices for devices that can act as a Stamp-controlled switch. Read Nuts and Volts Column #6 to see some examples of a Stamp controlling a switch that, in turn, controls something else.

    Post Edited (Mike Green) : 6/17/2010 2:30:14 PM GMT
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