This is the positive supply. It can range from 7V to 24V. In many circuits, this supply does dual duty: it powers motors and lights directly - perhaps being switched on and off by different circuitry. It is also used to supply the clean regulated 5V supply that some of the Block's electronics needs.

Never connect a +V connection to a 5V connection or any input or output directly. This will very likely damage the device, or since Blocks are very often closely wired together, all the Blocks in a system.

0 Volts, the electricity return path for all electronic circuits. Most sub-circuits that make up any form of electronics start from some positive voltage, pass through various components and end up connecting to 0V. Any voltage applied directly to 0 Volts is assumed to be a short circuit and should be avoided, so 5V and +V should never be connected directly to 0V. Also known as ground.

5 Volts, the supply voltage for many electronic circuits. When digital electronic circuits signal a logical true - or on value, it is by connecting an output to 5V.

In many Blocks, the 5V connection and other connections (digital inputs and outputs) will connect directly to some electronics that must have values between 0V and 5V and no more. If you put a higher voltage on these connections, you will almost certainly damage the device.

Having a continuous range of values. In Block systems, this value is normally between 0V and 5V.

Analog signals are provided by some kinds of sensors: light, acceleration, temperature sensors can all provide outputs that are continuous quantities, rather than being merely on and off.

Analog signals are required sometimes to convey data from one sub-system to another. Many Blocks exist that create and require analog signals.

Something that influences a quantity in the environment to a degree controllable by an electrical signal. Actuators exist that move things, illuminate things, etc..

The general actuator circuit appears below.

Here it is assumed that there is a Device that is set up to provide the control signal to the Actuator. The device provides 5V or +V and 0V in addition to the actuator to provide power. Most actuators can be thought of in this way - as requiring power and a control signal and delivering some kind of influence to the outside world.

The counting system that is like our own one ( 0, 1, 2, 3, 4, .. 10, 11, 12, ... 100, 101, 102, ...) except it only has two digits ( 0 and 1) , so counting is a little different (0, 1, 10, 11, 100, 101, 110, etc.)

An electronic device that can store electrical charge. Used in many places in electronics, for filtering, providing time constants, etc.

Capacitors are built in a huge variety of different ways and have several important specifications. Most important is the capacitance - measured in Farads. This is the amount of energy that can be stored by the capacitor. A very important secondary characteristic is the voltage at which it can store its energy.

A circuit is a configuration of electronic parts that allows them to actually do something. A circuit will include some kind of mechanism to provide energy to the electrons in the wires, causing them to want to flow from one side of the mechanism to the other, and some means of conveying them in a loop from one side to the other.

In the diagram above, the first circuit contains the proper elements: a source of power (a single cell) and the means to convey the power from one side of the cell to the other through the lamp, but the loop is not closed, so no current flows. In the second diagram, the wires are connected so electricity flows.

Electricity can be thought to flow from the positive side of the circuit to the negative side. Most electrical circuits are laid out with this kind of flow in mind. In actual fact, the means by which electricity is conveyed, the electron, is a negatively charged particle, so in fact electrons flow from the negative side to the positive side.

In most electronics, the circuit is a variation of the following:

Power issues from the positive terminal of a power supply and is conducted to the device that is to be powered. The electricity flows through that device, giving up its energy in the process to do useful things in the device then returns to the power supply. Care has to be taken that the power supply can provide sufficent current for the device.

A device might be simple internally - perhaps a light or a heating element, or it may be complex, containing many sub-circuits.

Power supplies can power multiple devices:

In this case both devices will receive the rated voltage of the power supply, and the total current will be the current consumed by both the first device and the second.

Devices can also be powered by multiple power supplies:

In this case, the device requires two different supplies. This might be because the device needs two different voltages (e.g. one for electronics and one for motors) or it might be that one supply is intended for delicate electronics and the other for less critical devices (like motors or lights). Note that the negative sides of the power supplies are connected together.

A graphical depiction of an electrical circuit that uses lines to represent wires, a handful of symbols to prepresent different components and plain rectangles to represent more complex devices.

Above are two representations of the same circuit, the first in a more pictorial version, and the second as a circuit diagram. Notice that the circuit diagram is much easier to generate and only retains the essential details of the circuit. The following symbols are used in the diagram. Lines are simply wires of some kind.

Cell

Lamp

Other symbols commonly used are set out below.

Button	Switch
Resistor	Capacitor
Diode	MOSFET
Potentiometer	LED
Photocell

The amount of electricity flowing at a point in a circuit. A tiny piece of electronics may require as little as a fraction of a milliamp of current to run (that is, a fraction of 1/1000 of an Amp), a large lamp, for example a car head light, might consume 10A.

Current can be either calculated indirectly or measured directly with an ampmeter or multimeter.

A DIP (Dual In-line Package) Switch is a tiny switch designed to be mounted onto a printed circuit board (PCB) to provide a way to configure a circuit.

An electrical connection made or disconnected by the user to configure some aspect of a circuit. It's made up of two parts, the header and the shunt. The header sits on the printed circuit board and makes a connection in the right place. The shunt can either be placed on top of the pins (joining them and therefore making the circuit), or not, in which case the connection is not made.

Often when the shunt is removed it is replaced on only one of the pins so it isn't lost.

Limit switches are switches connected to a mechanism to prevent it from damaging itself. Mostly, some part of the moving mechanism is designed to come into physical contact with the switch when its at the end of its travel. Ideally, the mechanism permits the motor to continue to move a little way beyond where the limit switch is activated to allow the motor time to stop moving.

Very short for metal-oxide silicon field-effect transistor. Special kind of transistor switch. When the Gate (G) terminal voltage is brought sufficiently high, current will flow from the Drain (D) to the Source (S) terminal.

Usually requires the Gate voltage to be 12V above the Source, but logic-level MOSFET's can work directly from a microprocessor output. MOSFETs are characterized by several values: their maximum voltage, their resistance when they're on and their maximum power dissipation. Be wary of manufacturer's claims about maximum current often these are exaggerated and require the device be kept at 25°C which often requires liquid nitrogen cooling...

Conventional DC motors have two wires and run when a current is passed through them. They are the most common kind of electrical motor. They come in many different shapes and sizes.

Most electric motors run at many thousands of revolutions per minute (RPM). In addition, the actual output is frequently not very powerful. To be useful for most applications, this raw output of the motor needs to be geared down. This provides a slower turning shaft with much greater torque.

Device for measuring voltage, current, resistance and sometime other quantities.

There are usually two probes that come with a multimeter.

To measure voltage, set the dial to Volts (V), put the black lead on the 0V, or the more negative side of the device you're measuring. Put the red lead on the point you wish to measure. You will get a reading in Volts.

To measure current, set the dial to Amps (A). You will also need to move the Red lead from the V & R input to the A input. Now put the multimeter in series with the device you are attempting to measure so that the current you are trying to measure flows through the multimeter. Be cautious, though, too much current can damage the multimeter.

Mathematical relation between the Voltage (V) flowing in a circuit, the Current (I) and the Resistance (R).

V = I R

An electrical arrangement where electrical flow is split between devices.

In this setup, any voltage applied to the top of the devices will appear at both devices since they're connected directly by low resistance wires. Total current flowing, however, will be split between the two devices.

Contrast this with series wiring.

A PIR (Passive Infrared) Sensor is what some people call a motion sensor. It detects changes in the location of infrared radiation sources in an environment. Since people are among the sources of infrared radiation this sensor can detect movement of people.

This is a powered sensor with three wires: +5V, 0V and the output. The output is a digital signal. Once triggered, the signal stays on for as long as there is motion and for a second or so afterwards.

Any source of power. Can be provided by battery, wall transformer, solar array, etc. Power supplies are marked with a plus (+) sign to indicate positive and a minus (-) sign to indicate negative. Conventional current is taken to flow from the + side to the - side. Note that if the power supply is a 12V supply, this means that if you measure the voltage across the terminals, you'll read something near to 12V. Usually the + side is connected to the + side of the device you wish to power - called +V in MakingThings products. The - side is connected to 0V or ground. See circuits for more about connections of power supplies and their relations to circuits.

In MakingThings products, there are frequently three different lines associated with power, +V, 5V and 0V. +V is usually between 7V and 24V and is used by many products to create the 5V power used by the electronics on the board. The raw +V can be used to power lights, motors, etc.

A power supply will usually have a voltage and a maximum current it can supply. Some wall transformer power supplies are simply rough converters from the 110 or 220V AC voltage. These are unregulated power supplies. Their voltages can range from significantly above the rated voltage down to significantly less, depending what is connected. Regulated power supplies, on the other hand contain electronics that can make sure the voltage being provided is constant under a variety of conditions.

Pulse Width Modulation is the technique used to compensate for the fact that creating true variable voltages in electronic circuits is not a simple matter. Switching something on and off is an easy matter, so sometimes when a varying signal needs to be created, a regular signal is switched on and off very quickly to simulate a varying voltage.

What is varied to create the effect is the proportion of the time the signal is on. If the signal is on 0% of the time the effective voltage is zero. If the signal is on for 25% of the time, a quarter of the voltage apears to be present. If the signal is on for 100% of the time, the full voltage (5V in our case) appears to be present.

PWM signals themselves aren't too useful, but sending them into switches to switch high current circuits makes them very useful. Then motors can be controlled and large lights, etc. Also, a PWM signal can be turned into a conventional analog one by the use of a very simple circuit (using a resistor and a capacitor).

A voltage that is kept very constant regardless of the load that is presented to it. Often created by a voltage regulator usually from a larger unregulated voltage.

Something that responds to a quantity in the environment by changing it's electrical characteristics. Sensors exist that can respond to light, heat, sound, vibration, acceleration, humidity, pressure, magnetism and many other qualities.

The general sensor circuit appears below.

Here it is assumed that there is a Device that is set up to respond to the sensor Signal. The device provides 5V and 0V to the sensor to power any internal electronics it might have. Many sensors can be thought of in this way - as requiring power (5V, 0V) and delivering a signal back to the device.

An electrical arrangement where power enters one device, leaves it, enters another, leaves it, etc.

In this setup, any voltage applied to the top of the device will be partially dissipated by the first device and partially by the second. This means that the voltage across each device may be different. Total current flowing, however, will be the same in each device.

Contrast this with parallel wiring.

Small motor capable of turning it's output shaft to specified orientations within a 90 degree circle. Usually runs from a 4 - 6V power supply and is controlled by short pulses the length of which control the shaft position. These pulses usually require special electronics to generate them - see the Servo Block

.

Mostly servos are used to control small movements - opening something, moving a part of an animated figure, etc. Most servos come with a variety of different attachments for the actuator.

Any situation where a portion of a circuit is connected to another in a manner that was not originally intended. This can be bad for many reasons: a short circuit can cause excess current to flow, causing damage to other elements in the circuit. A short circuit can also expose delicate devices to voltages in excess of their rated voltage capabilites. Microcontrollers and other digital electronics can be very easily harmed in this way. Finally, a short circuit can prevent signals from being transmitted properly. If an input is short circuited to 0V, for example, when another circuit tries to put a signal on the input, it will be connected directly to 0V and will not be able to send its signal and it may be damaged.

Common causes of short circuits:

Connecting a V+ wire or device connected to a V+ wire to a 5V terminal. This causes V+, which may be as much as 24V to be connected to the sensitve 5V power supply. This can expose any device on the 5V circuit to up to 24V. Most electronic devices are not designed to tolerate power supplies of much above 5V and they can easily be damaged this way.

Connecting a V+ wire or device connected to a V+ wire to a digital input or output. This causes V+, which may be as much as 24V to be connected to an input or output. If this input or output is connected to a microcontroller or other sensitive device, the input or output circuit may be destroyed..

Accidental wire contact. This can be caused if too much insulation is stripped away from a wire when it is screwed into a terminal and subsequently the device is moved, bringing the uncovered region of a wire into contact with another.

Improper mounting of PCB. PCBs frequently have many signals and voltages exposed on their bottom sides. Resting the board on a metallic object can cause these to be connected in unplanned and potentially damaging ways.

Accidental tool contact. Sometimes when using metal tools to make adjustments, the tools can make contact with exposed metal connections. This can sometimes be fairly benign, but if the wrong wires are shorted this can lead to the destruction of the device.

A kind of electrical motor which instead of continuously turning when voltage is applied, has distinct steps. To make it turn, its coils have to be energised in sequence.

A stepper motor usually has either four or six wires. The four wire variety is called a bipolar stepper motor. Those with six wires are called unipolar stepper motors.

Unipolar stepper motors have a structure as depicted above. There are four coils wound around two sets of armatures. The coils wound around the same armature (mostly) share a common wire.

A small potentiometer designed to permit adjustment of critical values in an electronic circuit.

Digital value corresponding to 5V (called "1" or "on" or "high") . Note that other systems may use voltages other than 5V for "true".

A voltage that is not smoothed by a voltage regulator of some kind. An unregulated voltage may drift from value to value depending on a number of circumstances. For example the peak voltage from an unregulated wall transformer may be significantly higher than specified, and it may even really be a 50 or 60Hz wave.

The electrical energy that is available at a connection or at a point in a circuit. Symbol : V.

Voltage is measured with a voltmeter or multimeter.

A voltage regulator is an electronic device that is capable of being supplied a potentially uneven voltage (unregulated) and providing a smooth voltage output. Voltage Regulators are used on many Blocks to take the potentially noisy and uneven +V signal and convert some of it into a clean +5V supply for the sensors, microcontrollers and so on, that require 5V.

Note in the illustration here, that the +V input can be quite unstable and the 5V output is perfectly clean. Note also that for very brief moments the +V may even fall below 5V, and energy stored in the regulator circuit's capacitor can supply the energy the circuit needs for those moments.

A wall transformer plugs into an AC outlet (110V in the US, 220V in many other places) and provides some other much lower (safer) voltage for use in smaller equipment. There are thousands of different models supplying a huge range of different output voltages. The MakingThings units tend to be 12V DC and supply 1A or 3A depending on the model.

Note carefully whether the transformer you have is regulated or unregulated. Some circuits require regulated voltages, others do not.

Wire is the means by which electricity is conveyed in circuits. It can take many forms. Usually there is a plastic covering called the insulation which can be removed with wire-strippers to reveal the conductor inside. Wires can be joined to each other and to other things by soldering or by other mechanical means.

Wire thickness is measured in AWG (American Wire Gauge) units. The bigger the gauge, the smaller the wire is. At MakingThings we use 30 gauge wire for tiny low current connections that are never going to need to physically flex, for example between two points on a printed circuit board. We use 22 gauge wire for connections that are going to need to be moved around a bit and for carrying moderate amounts of current (i.e. up to 2A for short distances). Finally, we use 18 or 16 gauge wire for high current needs.

We also try to use color coding for as many of the basic kinds of wiring as we can:

ORANGE - +V
RED - 5V
BLACK - 0V

The advantage to doing this is that it reduces the chances of confusing the wires and potentially damaging equipment.