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Description: MOSFETs are awesome. They're like a switch that you flip electronically! This MOSFET Power Controller makes it easy to switch a battery supply on and off using your favorite microcontroller. The board also has sewable pads so you can use it in e-textile projects that need more juice.

The MOSFET Power Controller came about because microcontrollers, like the Arduino or LilyPad Arduino, can only supply a limited amount of current. Sometimes, though, you want to control something that takes a lot of current like a fan or a heater (or a really bright LED). Simply connect a battery to the JST connector on the MOSFET Power Controller, connect the thing that needs power to the output, then connect one of the digital outputs of your microcontroller to the input pads. Now whenever you drive that pin on your controller HIGH, the battery will be connected!

The N-Channel MOSFET used in this design is rated for up to 30V and 6.5A although the board is really intended to be used at lower power. If you hook up anything beyond a 3.7V Li-Po battery, proceed at your own risk!

Features:

  • Control High-Current Loads
  • JST Connector makes Changing Batteries a Snap
  • It's Sewable! (Also has standard 0.1" spaced headers)

Documents:

Comments 13 comments

  • Aw, shucks! This is a low-side mosfet driver…I need a high-side mosfet driver using a n-ch and p-ch mosfet for an automotive application where the (-) battery terminal is chassis ground… guess I’ll have to lay one out myself…thanks anyway.

  • Why is hooking anything up beyond a 3.7v battery a risk?

  • This MOSFET is not specified for gate “ON” voltage < 4.5V. Therefore any Arduino variant which outputs 3.3V is unsuitable for directly driving it. Normal unit-unit variation in threshold voltage would let most units work at 3.3V and room temperature with light loads, but would not be good design practice for mass production. Also, the gate is unprotected against ESD. The resistor divider would help, if a five cent zener had been placed from gate to GND. Use thorough ESD precautions when connecting, especially as gate damage can show up much later.

    • The gate threshold voltage is guaranteed to be 3V max. With a gate voltage of 3.3V and using the Sparkfun PCB design, it should typically be able to handle up to about 3 amps, but at those levels it’ll run hot (too hot to be wearable). To keep the temperature below 100F (at 75F ambient and using 3.3V), the maximum current is about 1.6 Amps.

      • The 3.0V threshold is for only 250uA drain current, and increases typically 100mV at 0degC, so 3.1V. A 3.3V supply at -5% tolerance is only 3.135V. Even if the driving device had zero drop from supply to logic output HIGH, the small divider at the FET gate reduces applied voltage to 3.104V, leaving essentially no extra voltage to enhance the current beyond 250uA. Compounding the issue, the e-textile application often uses thin wires having more resistance, so drop in the GND wiring further subtracts from Vg-s.

        The saving grace is that the “typical” Vg-s(th) is only 1.7V, so the worst-case scenario is rather unlikely. This circuit would be flagged in a design review for a critical application.

  • can this be useful in creating AC output in an Inverter system

    • Probably not. The MOSFET is only rated for 30V and the resistor divider would slow the switching, causing extra power dissipation.

  • Hi guys, despite of the traces for output being wide looks like the connection between the MOSFET and the GND traces are really small ones. Looking at the pictures It seems to be a very weak point of the design. :(

    • That ground trace is only there to provide a reference. If the board is hooked up properly, that trace should conduct nearly no current.

    • How thick do you think the connections inside the IC are? They did suggest using nothing higher than a 3.7V Li-Po. Check he datasheet and/or a trace width calculator. It is within spec.

    • Correct me if I am wrong, but those large pads are there for attaching conductive thread, not for extremely high current outputs. You are still limited by the size of the pins on the IC, and the traces going to the wider contacts look around the same size of the pins on the MOSFET.

      • Current capacity is a volume thing. The pins on the IC typically have much more volume (height? depth? not sure what the right geometrical term is) than a copper trace on a PCB board will. For high power routing you will typically wind up with traces wider than the pin width with solder acting to distribute the charge from the pin to the wider trace.

        • It’s a crosssectional thing, and current plays the role in the power equation. P=iv, where your power is proportional to the heat capacity of the wires/connections. That’s why connections usually fail at either the connection interchange or ~30% of the length within a long connection. Also note you need to account for not only your steady state response, but transient response of your system (transient will see spikes in amps, which spikes power, which spikes power capacity of the wires due to their thermal properties).


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