How not to make a badge for an event.

Every year I make a badge for the Nottingham Gaussfest

Previous years I have just done a simple laser cut badge with a battery powered flashing LED, but this year I thought I’d do something a bit different.

My first idea was pushing the boat out a little too far, and after receiving the PCB’s I realised it would never work ( I don’t want to say what it was, as I have ideas for sort it in coming years)

So, as I was losing time quickly, I decided that I’d build a simple lightning detector. At the Gaussfest there are many, many machines that make sparks. So the idea was, when the exhibitors are making sparks, their badge lights up, what could be easier.

If I was going to do this, the badges MUST be there and working on the day. No point in having a lightning detector badge on a non-teslacoiling day.

I roughed up a circuit, based on Extreme kits lightning detector. To keep the LED on for a few seconds I used an NE555 timer.

The circuit was tested on bread-board and if I used a CMOS NE555 would run really well with a 3V supply. (Non CMOS 555’s need 6v AND take a lot more current)

I wanted to use through-hole as Extreme Kits’s lightning detector circuit used almost all of the same components but, I didn’t want ugly through hole wires on the front of the PCB, so I opted for through hole components, but surface mounted.

Happy with the circuit, I edited the PCB layout so I could get two boards in a 10x10CM order, which is the most cost efficient way of getting these PCB’s made with my supplier.

I also ordered 50 NE555 (CMOS) as the best prices came from china the PCB’s and the chips should arrive at roughly the same time.

After a couple of weeks the PCB’s and chips arrived and I quickly built one up and put in a CR2032 3v battery

It didn’t work, nothing…

Nothing I did would make it work, but everything seamed fine. Eventually I put it onto my PSU and tried it at 3V from there.

Nothing.

Scoping the output, it worked, but wouldn’t drive the LEDS, I tried every variation of LEDS I had, nothing worked (apart from a VERY dull glow).

On a hunch, I tried the circuit at 6V

Everything worked fine. Eh ???

I then occurred to me that my CMOS NE555’s (from China) may not be CMOS, I swapped one for a lone known good chip I had, the circuit worked fine. (insert swearwords here)

With not enough time to reorder CMOS 555’s, I needed a solution.

Well, CR2032’s are 3v and 3.2mm thick, CR2016’s are 3v and 16mm thick, I could fit two 2016’s in a 2032 socket giving me 6V. This worked, but the bottom battery would short. A small piece of tape sorted that quickly. The only down side now is that 2×2016’s have half the current capacity of 1×2032 and the non CMOS 555 chips are a lot more greedy. In a trial, the badges lasted 14 hours. I only needed them to last 8. I was hoping for a few days where I could put in the batteries and pack the badges. Adding a pull away tab which could turn them on, on the morning of the event sorted that. Finally I had a solution.

So, I built a batch of the PCB’s

Half of them worked, the other half refused to do anything. (insert other swearwords here)

On closer inspection the second PCB on each panel wouldn’t work.

Referring back to the PCB design I spotted my error, The fills would against ground, as I’d copied the PCB the signals for GND were no longer GND so the fills avoided the pads. All the GND connections were not connected. I didn’t have time to reorder the PCB’s

Luckily, my PCB house had done a couple of extra PCB’s, so I had JUST enough. The two organiser badges though, had a pretty addition of gold wires on the back joining all the GNDS together.

Finally a box of working badges, with only a few days to go. The only problem was I ran out of time, and I never got to test the badges with a real tesla coil or Wimshurst.

Luckily on the day they performed pretty well, If I was going to be harsh, they triggered occasionally on static discharges with peoples clothes, and their range was poor when they were close to the chest, but 1-2M away from my and other tesla coils they lit up wonderfully.

A badge being triggered by a discharge from my Shake sphere (that’s the background noise)

So my tips for designing a badge for an event.

• Start early.
• Nope, earlier.
• Order the components and PCB’s and test them all, while you still have time to reorder.
• Have a backup plan.
• it will cost more then you think, budget.
• Put a power switch on your badge. They are cheaper in time than messing with pull out tabs or populating batteries.
• If something goes wrong, don’t panic, there are many people out there who may be able to help.

          What is a Gaussfest ?

Nottingham Gaussfest is a yearly meeting of a loose group of friends sharing a common interest in high voltage equipment and Tesla coils.In the USA these meetings are always referred to as Teslathons, a reference to Nicola Tesla who’s tesla coils always feature prominently at these events. We decided, being European, we would adopt Carl Friedrich Gauss as the scientist, due to all the devices also required a high magnetic field and we wanted to differentiate ourselves. Hence the term Gaussfest.

The equipment that appears at the Gaussfest is entirely dependent on the Exhibitors present, and their current interests. Usually there will be a collection of various types of Tesla coils, and a collection of static electricity generators like Van-De Graff machines and Wimshurst machines. But each year someone surprises me with something different, or new.

Tesla coils are the most common high voltage device we get, are essentially a large transformer. Near the bottom of the tesla coil is a radio frequency generator either electronic or mechanical, driving a primary winding with a small number of turns. The Secondary coil (the tall one) has a much larger number of turns of around 800-2000 turns typically. And at the top if this, a topload where the high voltage comes out. We get tesla coils of all sizes from a 50mm high, to over 2M tall at the Gaussfest.

The Static generating machines our exhibitors bring are even more are varied. The common ones are a Van de Graaff machine, uses a belt to transfer charge up to the top dome where it is stored, and the Wimshurst machine uses a pair of contra-rotating disks to multiply charge and store it into a pair of capacitors. Again the sizes of these machines vary from 200mm tall to 1.5MAlthough the electrical discharges from these machines look dangerous, they are entirely safe if viewed from a distance, and our exhibitors are very experienced with the operation of their machines.

Or Exhibitors are happy to talk about how their machines work and the problems with their construction, although if they are preparing them for a demonstration, or have problems please give them “thinking room” as their safety, and the safety of their equipment is paramount. All our exhibitors are all amateurs and make and demonstrate high voltage equipment for fun. The Gaussfest is their opportunity to display what they have been working on.

Commercial high voltage engineering is expensive, due to this many of the exhibits on display will have been made totally or partially from household items, surplus, and any available electronic equipment, often with items multiplied up to deal with the high voltages/currents that are required. To keep the cost down, the equipment is usually run at the very maximum of its tolerances. These devices are rarely engineered for their longevity, so failures are quite common, and this trade-off is very much part of the hobby. Due to this, we do not have planned schedules for the demonstrations, as equipment WILL FAIL (and be repaired) during the day, although we will endeavour to have something always happening.

When the Gaussfest moved to Papplewick in 2017, we were very conscious that for us to do our activities, Papplewick pumping station must get something back, So Papplewick allow us to meet, and we let the public see what we do and give demonstrations to give back to the Pumping station. As much of what we do can be dangerous, this trade-off is some restrictions in access to the station to ensure your safety.  

Nottingham Gaussfest

Gaussfest registration

Key in the dark has been played in Scout groups and youth groups for as long as I can remember.

The idea of the game is one Scout is blindfolded and sat on a chair with a large set of keys underneath. He is “armed” with a torch. Usually a number of obstacles and places to hide are set up around them.  The rest of the scouts need to stealthily get to the keys without the Scout shining the torch on them.  If they are hit by a touch beam they are defined dead and have to either sit out the game, or start from the beginning again. The idea is that any sound made by the scouts in their approach means a torch shone their way.

Of course in practice a torch is not the ideal “weapon” although rules are that the torch is only to be used intermittently, it is basically an infinite resource and is usually shone around with abandon. Plus the operator being blindfold, they have no idea if the touch is on or off. The other main problem is that the torch beam diverges so much that multiple asalients can be cought at once.

So I started to look at alternatives. As 5W leds are cheap I thought of one of these as a source, combined with a 10 x 70mm focal length lens from a watchmakers eyeglass (loupe) in a 20mm tube. I could get a pretty narrow, bright beam.

Mounting the LED on a piece of copper allowed for any heat from the led to escape. 

Of course, I needed a way of switching this, so I used a MC4427 1.5A mosfet driver, purely as it was a single chip solution and mainly as I had one to hand.

I dead bug soldered it, as there were only 4 connections. and glued the driver to the back of the heatsink.

I had had the idea of “charge” to keep down the number of flashes, the idea being that every press of the button would freeze out the user for 0.5 Seconds. To show this, I thought of a number of neopixels along the barrel. So these were attached with some acrylic rings to spread the light out 

Whilst I was thinking about the design of this, I was given an Adafruit Feather Huzzah 

This was ideal, as it had a Lipo PSU and charger built in, and plenty of IO, coupled with a 25mmx9mm LIPO battery it gives loads of power..

Plus If you use MicroPython you got the neopixel support.

Realising that the operator would be blindfolded, I wanted some feedback so they would know when the torch was used. After trying a solenoid, I found this had two problems. 1. It was power hungry. 2. It took up a load of space.  So I went back to a large’ish vibration motor (also to hand)

I had decided that the whole thing should fit in a tube no more than 40mm in diameter, so I laser cut some supports and hung the whole lot from two m3 threaded bars. After many attempts I finally got the acrylic into pieces that would support the electronics and battery and assembled the whole thing together. 

Of course, I’d forgotten the buttons. These needed to be at the front, but so the case could be removed they needed to connect at the back.

After a couple of attempts with internal wiring, that got cought up either putting it together or taking it apart. I eventually put the wires on the outside, covered the whole handle, wires and everything in leather and connected the buttons with a cable at the back.

The USB cable for power (and programming) currently exits out of the back, but is soon to be replaced with a micro socket.  There is also a small switch for the units power.

The next addition was a burst fire mode, you get 5 shots in quick succession, but it takes longer to recharge.

I also added an auto power off, if left for 60 seconds.

Circuit Diagram [gview file=”http://www.extremeelectronics.co.uk/wp-content/uploads/2018/04/kitd.sch_.svg”]

Final Touches…

End plate with USB charging port and On off switch.

Unfortunately as I take the power for the motor, Neopixels and the main LED straight from the battery Powering down is a two stage process. First you press and hold both buttons. After a few seconds everything is turned off. Then you can switch off the uP. I do it this way as  I don’t have to switch everything on to charge it.

The finished Torch

Code

[code]

import machine, neopixel, time, utime

np1 = neopixel.NeoPixel(machine.Pin(12), 8)
np2 = neopixel.NeoPixel(machine.Pin(13), 8)
LED5w = machine.Pin(14, machine.Pin.OUT)
B1 = machine.Pin(5, machine.Pin.IN, machine.Pin.PULL_UP)
B2 = machine.Pin(2, machine.Pin.IN, machine.Pin.PULL_UP)
vib = machine.Pin(4, machine.Pin.OUT)

LED5w.off()

firec=(255,255,255)
chargec=(0,20,0)
black=(0,0,0)

OffTime=60

def fire(fx):
for x in range(0,fx,1):
for a in range(8):
np1[a]=firec
np2[a]=firec
np1.write()
np2.write()
time.sleep_ms(4)
np1[a]=black
np2[a]=black
np1.write()
np2.write()
LED5w.on()
vibrate()
time.sleep_ms(100)
LED5w.off()

def charge(cx):
for a in range(8):
np1[a]=chargec
np2[a]=chargec
np1.write()
np2.write()
time.sleep_ms(cx)

def vibrate():
vib.value(1)
time.sleep_ms(70)
vib.value(0)

charge(63)
start=utime.ticks_ms()

while(B1.value() or B2.value()):
if not B1.value():
fire(1)
start=utime.ticks_ms()
charge(63)
if(not B1.value()):
time.sleep_ms(1000)

if not B2.value():
fire(5)
start=utime.ticks_ms()
charge(350)
if(not B2.value()):
time.sleep_ms(3000)

if ((utime.ticks_ms()-start) > OffTime*1000):
for a in range(7,-1,-1):
np1[a]=black
np2[a]=black
np1.write()
np2.write()
time.sleep_ms(50)
np1[0]=(0,0,10)
np1.write()
while(B1.value()):
time.sleep_ms(200)
start=utime.ticks_ms()
charge(63)

vibrate()
for a in range(7,-1,-1):
np1[a]=black
np2[a]=black
np1.write()
np2.write()
LED5w.off()

[/code]