Before you walk in
Prepare
Most of every class is bench time, and bench time is the expensive kind: the room, the kit and the technician are all there at once. Every block below says what you must already be able to do, three things to actually go and do, and what to bring.
What Electricity Does in a Theatre
What you must already be able to do#
Nothing electrical. This class assumes no prior electronics at all. It does assume arithmetic you can do without a calculator: multiply and divide by ten, rearrange a = b × c into b = a ÷ c without looking it up, and read a number written as 4.7 kΩ or 470 µF and know which is bigger.
If any of that is shaky, spend forty minutes on Foundations first. It is the cheapest forty minutes in the course. Everything after Class 3 assumes it silently.
Three things to do#
- Find the distribution board for a space you already work in, and photograph the labelling. Do not open it. You are looking at what is written on the door: circuit numbers, ratings, what each way feeds.
- Write down three things you have plugged in this month and guess what each one draws in watts. Guess. We will check them in class and the gap between your guess and the truth is the lesson.
- Read the safety card once, end to end. You will not remember it. Read it anyway, so that when it comes up in Class 15 it is the second time.
What to bring#
A notebook you are willing to write measurements in and keep for sixteen weeks. Not a phone. The act of writing a number down is half of what makes you check it.
Measure, Test, Prove
What you must already be able to do#
Say what voltage, current, resistance and power each do, in your own words, without the formulae in front of you. Rearrange V = I × R in both directions. Explain why a voltage reading needs two probes and a resistance reading needs the circuit dead.
If Class 1's bench work did not happen for you, read its bench section and do Block A at home with a battery and a torch bulb before you arrive. Two hours of today is measurement, and there is no way to catch up during it.
Three things to do#
- Buy or borrow a multimeter and bring it. The kit list says exactly what to look for and what to avoid. You need a meter with a fused current range and a CAT rating. A five dollar meter with no fuse is not cheaper, it is a different product that happens to look similar.
- Find the fuse in your meter. Open it, look at it, close it. Know its rating before you need to know it, which will be about ninety minutes into today.
- Measure three batteries in things you own, and write down the reading, the rated voltage, and whether the thing still works. A AA cell at 1.2 V is not the same story as one at 1.5 V.
What to bring#
Your meter, your notebook, and a set of probes you have looked at closely enough to know whether the insulation is intact.
Components and Connectors
What you must already be able to do#
Use a multimeter in all four modes without thinking about which jack the red lead is in. Test a cable with the five-step procedure from Class 2. Rearrange Ohm's law. Read 4k7, 470R and 0.47 µF and put them in order of size.
Three things to do#
- Take apart something dead. A broken phone charger, a failed LED lamp, an old radio. Do not plug it in, and if it has a large capacitor in it, treat that capacitor as live. Photograph the board and bring the photograph.
- Find five different connectors in your building and photograph each one. Not five of the same. You are looking for the range: audio, data, power, mains, and something odd.
- Read the resistor colour code and get ten right in a row on the tool. It takes about fifteen minutes and it saves you an hour every week for the rest of the course.
What to bring#
Your meter. A phone with a camera and a torch. Reading glasses if you use them, because half of today is reading markings that are 1 mm tall.
Soldering and Fabrication
What you must already be able to do#
Identify the common components and read their markings. Test a cable with the five-step procedure. Know which pin of an XLR is which without looking it up.
Nothing today requires calculation. It requires that you have watched somebody solder, so that the first joint you make is not the first joint you have seen.
Three things to do#
- Watch two soldering videos and notice the disagreement. They will contradict each other on tip temperature, on flux, and on whether to tin the wire first. Come with the contradiction written down and we will resolve it at the bench.
- Find out what your fingers do. Hold a pencil like a soldering iron for two minutes without resting your hand on anything. If your hand shakes, that is normal and it is why the first thing we teach is where to put your elbows.
- Check the kit list and get your strippers. Not a knife. A knife nicks strands and a nicked strand is a cable that fails in week six.
What to bring#
Safety glasses, which the department has but yours will fit better. Tie long hair back. Do not wear anything you love, because solder spits and flux stains.
Loads, Switching and Isolation
What you must already be able to do#
Calculate an LED series resistor without help. Explain the flyback problem in one sentence. Read a resistor. Use P = I² × R. Terminate and test a cable, because from here on you will be building things that plug into other things.
Three things to do#
- Find three relays in your building and photograph the label. Coil voltage, contact rating, number of poles. They are in the dimmer rack, in the HVAC panel, and inside almost every piece of equipment with a hard on-off.
- Look up one MOSFET datasheet —
IRLZ44Nis a good one — and find three numbers on it: V_GS(th), R_DS(on), and the continuous drain current. You will not understand all of it. Find those three. - Write down what you think happens if a microcontroller output is connected straight to a relay coil. One paragraph, your best guess, brought to class. We compare guesses to the oscilloscope trace.
What to bring#
Meter, notebook, and the cables you made in Class 4.
Build a Driver Board
What you must already be able to do#
Solder a consistent joint. Calculate an LED series resistor. Explain why a flyback diode exists. Say what V_GS(th) and R_DS(on) mean and why a logic-level MOSFET matters. Test a cable properly.
This class assumes Class 4 and Class 5 both landed. If either did not, say so before we start rather than three hours in.
Three things to do#
- Read the schematic, which is on this page and in the pack. Not skim: read it, and write down every component you cannot account for. Bring that list. It is the most useful thing you can bring.
- Work out the two resistor values yourself before you arrive: the gate pull-down and the LED series resistor. Show the arithmetic. We compare answers at the start.
- Decide your own test plan. Three tests that would prove the board works, and one test that would prove it is safe. Write them down before you build, because writing them afterwards is how you accidentally write tests that your board happens to pass.
What to bring#
Everything. Iron skills, meter, safety glasses, notebook, and the cables from Class 4.
Analogue Signal, Impedance and Grounding
What you must already be able to do#
Ohm's law, fluently. RC time constants. Series and parallel. What a capacitor does to AC and to DC. Why the return path matters, from Class 1.
Three things to do#
- Make something hum. Connect a laptop's headphone output to a powered speaker, with the laptop on its charger. Then unplug the charger. If you hear a difference, you have just reproduced the most common fault in the industry, and you should come able to describe what you heard.
- Find the ground lift switch on a DI box or an audio interface. Photograph it. Read what the manual says it does, which will be vague, and come with a question about it.
- Write down what "impedance" means to you now, in one sentence, before the class. Keep it. At the end, write it again. The two sentences will differ and the difference is the class.
What to bring#
Meter, notebook, your XLR cable from Class 4, and headphones you trust.
Hum Hunting and Scope Work
What you must already be able to do#
Explain a ground loop as a circuit, not as a phrase. Say what balanced means and where the cancellation happens. Convert between voltage ratios and decibels for 6 and 20 dB. Calculate an RC time constant.
Three things to do#
- Find a hum somewhere real — a rehearsal room, a studio, a friend's setup — and write down five things about it before you try to fix it: is it a hum or a buzz, does it change with the volume control, does it change when you touch the connector, is it present with nothing plugged in, and does it change when the lights are dimmed.
- Watch a fifteen minute oscilloscope tutorial and write down the four controls you will need: volts per division, time per division, trigger level, trigger source. Everything else on the front panel can wait.
- Predict what mains looks like on a scope. Draw it. Include the amplitude in volts. You did the arithmetic in Class 1 and most people still draw it wrong.
What to bring#
Meter, notebook, headphones, and your XLR cable.
Data, Protocols and Networks
What you must already be able to do#
Use a scope: timebase, trigger, coupling, single shot. Terminate a 5-pin XLR and an RJ45. Explain what impedance matching means and why RF is the exception to bridging.
Three things to do#
- Count the data cables in one venue. Walk a space and write down every kind of data cable you can find: DMX, network, MIDI, USB, HDMI, SDI, fibre. You are building a sense of how many parallel conversations a modern building is having.
- Find a DMX terminator and photograph it. Then find a DMX line that does not have one, which will take about four minutes.
- Read your lighting console's patch page and work out how many universes it outputs and what protocol it uses to get them to the rig. If you cannot find out, that question is a good one to arrive with.
What to bring#
Meter, scope skills, notebook, and the DMX cable you made in Class 4.
Build and Break a Rig
What you must already be able to do#
Everything from Class 9: the DMX packet, termination, topology, the difference between state and event protocols. Terminate a 5-pin XLR and an RJ45. Use a scope with a trigger.
Three things to do#
- Draw a rig from memory. Any rig you have worked on. Console, splitter, runs, fixtures, addresses. It will be wrong and incomplete, and finding out where is the point.
- Write down five DMX symptoms you have seen and what somebody told you the cause was. We will check those attributions today, and several will turn out to be folklore.
- Learn to draw a rig properly. Look at one real lighting plan and one real signal flow diagram, and notice what a signal diagram includes that a lighting plan does not.
What to bring#
Meter, notebook, your DMX cable, and patience. This class is deliberately frustrating for about forty minutes in the middle.
Microcontrollers
What you must already be able to do#
Calculate an LED series resistor. Explain a pull-down resistor and why a floating input is not off. Drive a MOSFET. Use a scope with a trigger. Read a schematic.
Three things to do#
- Get a board and blink an LED on it before you arrive. Any Arduino-compatible board. Install the toolchain, connect it, load the blink example, change the interval to 200 ms. That is all. If the toolchain fights you, it will fight you for the first hour of class instead, and the toolchain is not what we are here to learn.
- Write down what
delay(1000)actually does to the chip. One sentence, your guess. Bring it. - Find a microcontroller in a piece of show equipment. Open something dead and find the chip with a crystal next to it. Read its part number and look up what it is.
What to bring#
Your board, a USB cable that carries data (not a charging-only one, which wastes the first ten minutes of every class of this kind), a laptop with the toolchain working, breadboard, meter.
Program a Prop
What you must already be able to do#
Blink without delay(). Debounce a switch. Read an ADC. Drive a load through the Class 6 board. Explain a pull-down and what happens to your input when its cable is cut.
Three things to do#
- Write the
millis()blink from memory, without looking it up. If you cannot, write it out three times. It is the skeleton of everything today. - Describe a prop you have seen fail in one paragraph: what it did, what it should have done, and what you think the cause was.
- Draw a state machine for a kettle. Off, heating, boiled, and what causes each transition. Five minutes. It will make the middle of today much easier.
What to bring#
Board, laptop, your Class 6 driver board, meter, breadboard, and a USB cable that carries data.
Sensors and Actuators
What you must already be able to do#
Read an ADC and know its resolution and its limits. Build a voltage divider and calculate its output. Drive a load through the Class 6 board. Write a state machine. Explain why an impossible reading is a fault.
Three things to do#
- List five things a show needs to know. Is the trap open, has the actor reached the mark, is the flying piece at its low point, is the door closed, is the smoke machine hot. For each, write what would have to be measured. That translation is the class.
- Find a limit switch somewhere in the building and look at how it is mounted. Notice whether it is arranged to be made when safe or broken when safe. There is a right answer and about half of installations get it wrong.
- Watch a servo and a stepper move in any video and write down two differences you can see.
What to bring#
Board, laptop, driver board, meter, and the state machine you drew in Class 12.
Build a Triggered Effect
What you must already be able to do#
Everything from Classes 11, 12 and 13. A state machine on paper. Debounced inputs. An ADC reading with range checking. Driving a load through your Class 6 board. Normally closed safety wiring.
Three things to do#
- Choose your effect and write one sentence about what the audience sees. Not what it does electrically. What the audience sees. If you cannot write that sentence, you are not ready to build it.
- Draw the state machine and the failure table before you arrive. The failure table is four rows: power-up, control lost, sensor out of range, and reset.
- List your parts and check the department has them. A build class where you discover at hour two that there are no 12 V solenoids is a build class you spent watching.
What to bring#
Everything you own from this course. This is a full build.
Safety Systems and Fault-Finding
What you must already be able to do#
Normally closed wiring and why it exists. What earth is for. Series and parallel. Everything about loads, switching and isolation from Class 5. The half-split method from Class 8.
Three things to do#
- Find every emergency stop in one venue and photograph each one. Then work out, or ask, what each one actually stops. The answers will surprise you: some stop less than people believe, and that gap is the most important thing you will learn this week.
- Read the safety card properly this time, all of it. Third reading.
- Write down one near miss you have witnessed or heard about. What was the last point at which it could have been prevented? That question is the whole of safety engineering.
What to bring#
Meter, notebook. This class has a demonstration on real mains, which you will watch.
Capstone and Fault-Finding Exam
What you must already be able to do#
All of it. This class assesses the whole course and adds nothing new.
If there is one thing to revise, revise the method: establish the boundary, half-split, one change at a time, prove the fix. More marks are lost to disordered searching than to missing knowledge, every year, by a wide margin.
Three things to do#
- Build your capstone piece in advance. You do not build it today. You bring it finished, documented and working, and today you prove it and defend it.
- Write your documentation sheet and test it on somebody outside this course. Give them the sheet and the device and say nothing. Every question they ask is a defect in the sheet.
- Re-read your own fault logs from Classes 8, 10 and 15. Your own record of what took you longest is a better revision aid than any summary, because it is specific to how you actually search.
What to bring#
Your capstone piece, its documentation, your meter, your notebook with every log in it, and the cables you made in Class 4.