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Step 3Parts: Electronics
You need four electrical components. I will be describing these very briefly, but ultimately I will have to leave it to you to make your own educated decisions on which components to use (or use exactly the same ones that I did).
A transistor
Choosing the right transistor for a project is a whole book in itself. Fortunately, for this project, most transistors with a pulse current rating of at least a few amps, and an hFE above 40 should probably work. I'm using a BDX53B Darlington transistor which I had lying around from other projects, it's not ideal, but it does the job. A TIP29 transistor would probably also work.
If you are using a MOSFET, you should add a pull-down transistor of about 1k after the gate resistor, otherwise the pull-up current of Forebrain in programming mode may be enough to fire the MOSFET.
If you don't know your transistors, I would suggest learning about how to choose the right transistor or asking someone about whether a certain transistor is suitable for this application or not before continuing, as the wrong choice might not work, damage something, or in the worst case blow up in your face.
A capacitor
A largeish aluminium electrolytic capacitor is required to supply some of the peak pulse currents required when the solenoid activates. The voltage rating must be above 5V, and I would recommend at least 470uF. I am using a 10V 2200uF capacitor
A diode
A diode is necessary to avoid flyback voltage spikes when the solenoid is switching. I'm using a 1N4004 general purpose diode
A resistor
Is needed to allow the microcontroller to drive the transistor. The value you should use depends on the the transistor you are using, if you don't know which resistor to use, I would suggest that 150ohms would probably work for most BJT devices, or 10ohms for a MOSFET. I am using a 150ohm resistor
A transistor
Choosing the right transistor for a project is a whole book in itself. Fortunately, for this project, most transistors with a pulse current rating of at least a few amps, and an hFE above 40 should probably work. I'm using a BDX53B Darlington transistor which I had lying around from other projects, it's not ideal, but it does the job. A TIP29 transistor would probably also work.
If you are using a MOSFET, you should add a pull-down transistor of about 1k after the gate resistor, otherwise the pull-up current of Forebrain in programming mode may be enough to fire the MOSFET.
If you don't know your transistors, I would suggest learning about how to choose the right transistor or asking someone about whether a certain transistor is suitable for this application or not before continuing, as the wrong choice might not work, damage something, or in the worst case blow up in your face.
A capacitor
A largeish aluminium electrolytic capacitor is required to supply some of the peak pulse currents required when the solenoid activates. The voltage rating must be above 5V, and I would recommend at least 470uF. I am using a 10V 2200uF capacitor
A diode
A diode is necessary to avoid flyback voltage spikes when the solenoid is switching. I'm using a 1N4004 general purpose diode
A resistor
Is needed to allow the microcontroller to drive the transistor. The value you should use depends on the the transistor you are using, if you don't know which resistor to use, I would suggest that 150ohms would probably work for most BJT devices, or 10ohms for a MOSFET. I am using a 150ohm resistor
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