OK how does it work and can a Picaxe do it?

Andrew Cowan

Senior Member
I don't like the way that there is a slight delay between turning on the switch, and the bulb lighting. It is espesially visible in the video with the yellow bulb (1.03 mins).

Andrew
 

hippy

Senior Member
The delays between switching and lighting are unbelievably long in that version and the fifth switch adds suspicion as well - Why would you need a power switch if the switches turn off all the lights ?
 

Andrew Cowan

Senior Member
Exactly. My power switch is a slide switch in the base - and because it is so small, no one I've met believes there could be a chip inside. I planned to run it off a 9V battery, but the lamps (4x300ma=1.2A) means rechargable AAs are needed.

Andrew
 

Mycroft2152

Senior Member
Andrew,

Congrats on your scholarship!

SMD is not that difficult to use, it just takes a steady hand and a lttile care.

Remember. for the PICAXE SMD chips, you will need a way to program them, unless you built that function board.. the downloading connector will take up more room than the chip :)

Myc
 

womai

Senior Member
Andrew,

first, congratulations for the scholarship.

Second, SMD isn't that hard (at least SOIC packages, which is what the Picaxe SMD version is). Actually may be easier for homemade boards, because it means less holes to drill. I looked at the pictures of your PCB and would say you should have the technical skill to cope with the somewhat smaller line width (0.05 inch for SOIC vs. 0.1 inch for DIP).

Wolfgang
 

Andrew Cowan

Senior Member
I use homemade boards and school-made boards (neater) for PCBs. My school can produce SMD boards (although I only know of one person using them). I have lots of salvaged SMD components, so I may get my teacher to make a board with lots of SMD components on it, so I can practice with it.

My homemade PCB making process is simple, but effective:
- Print artwork onto acetate.
- Using a UV light box, print mask on to a photo sensitive PCB
- Develop
- Etch in bubble etch tank with ferric cholide.

Although this sounds expensive:
- The UV light box is an MDF box with a fly-killer UV tube in it (cost about £10). Works as well as my school's £150 light box.
- The bubble etch tank is a plastic container with some plastic tube with holes in it. This is then connected to a 5V air pump. Overall cost about £10. Works (almost) as well as my school's £200 one, although I wish my homemade one had a heater in it.
So you can make homemade PCBs very cheaply!

Wolfgang - don't look at that PCB! I did it in a rush - it is much less neat than my PCBs normally are.

What do most people do for downloading programs to SMD picaxes? solder on the three wires when needed?

I like the idea of using ULN2003s transistors in parallel on veroboard, although I don't tend to use veroboard much, because I can get good PCBs made at school (for free) in a day, and PCBs are generally simpler than veroboard.

Thanks,

Andrew
 

eclectic

Moderator
"although I wish my homemade one had a heater in it."

Inside-out logic?

Put the tank IN a bowl of hot water?

Photographers have done this for MANY years!

e
 
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Andrew Cowan

Senior Member
Not a bad idea! Other 'enthusiasts' I have spoken to on the internet suspend a 240V light bulb above the ferric cholride, but I can't do this as I use a plastic tank.

Putting the tank in hot water seems obvious now...


"Photographers have done this for many years"

...then I probably shouldn't tell him that I have been running photography club at school for the past 4 years, and we heat our chemicals with a hot water bath. No. I won't tell him that - it might make me look foolish...
 
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kevrus

New Member
Andrew, you made a nice job of your magic box.
On the subject of making PCBs, for an etching tank I use a plastic 'cereal' container with a fish tank heater and a fish tank pump with aerator stone for the bubbles. I no longer use ferric chloride and now use sodium persulphate, less messy and the etching process can easily be monitored as the board can be seen through the clear solution..turns a nice turquoise/blue when some etching has taken place.
 

Andrew Cowan

Senior Member
Andrew, you made a nice job of your magic box.
On the subject of making PCBs, for an etching tank I use a plastic 'cereal' container with a fish tank heater and a fish tank pump with aerator stone for the bubbles. I no longer use ferric chloride and now use sodium persulphate, less messy and the etching process can easily be monitored as the board can be seen through the clear solution..turns a nice turquoise/blue when some etching has taken place.
I think I have a packet of sodium persulphate in a cupboard, I just need to mix it up. I am thinking about replacing my PCB tank - I am just searching for a tall plastic tub with a rectangular cross section. With the lid on the tnak when not in use, how long does a solution of sodium persulphate last? Or doesn't it do bad over time?

Fish heater... fish pump... now you just need the fish!

Andrew
 

alpacaman

Member
My version

I really like to see how others do these kind of projects.
Here is the front and back of mine. I used white LEDs and used pieces of colored straws over the LEDs and switches.
I also tried to make it so you can see, or at least think you can see, the wiring. The PICAXE is inside the battery box. The battery box is for 4 AA cells but I'm only useing 3. The place for the 4th battery holds the PICAXE. The circuitry is all hand wired to make it as small as possible so it could fit inside the battery box.
Don't look too closely at me wood working abilities.
 

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hippy

Senior Member
Excellent idea using straws for colour sleeves and that's a very clever way of making it look like the wires run direct from switch to LED.
 

kevrus

New Member
I think I have a packet of sodium persulphate in a cupboard, I just need to mix it up. I am thinking about replacing my PCB tank - I am just searching for a tall plastic tub with a rectangular cross section. With the lid on the tnak when not in use, how long does a solution of sodium persulphate last? Or doesn't it do bad over time?
This is my first solution of this which I made up about 9 months ago and it's still working ok, hav'nt done a large quantity of boards but I am more than happy with it's performance to date....I heat it to 40deg C fo the etching.

Fish heater... fish pump... now you just need the fish!
maybe a picaxe controlled robot fish??
 

Dippy

Moderator
I use sodium pesulphate too. Lots less messy and that lovely blue.

Also if you water down the exhausted solution by 50 to 1 it makes good moss-killer.

Still got it after 9 months? You can't do much etching.

Oh, and when you stain your socks, trousers etc with Ferric Chloride go to the chemist/pharmacy and get some oxalic acid, make up a real strong solution and paint it on the offending part. Works well, but CAUTION, very toxic. Not for schoolboys. I mean that seriously!! (It's also a superb bath for derusting things).
 

Andrew Cowan

Senior Member
That is brilliant, alpacaman, although with my one, it is easy to get the ten second reset time my unscrewing bulbs. How long is your reset, and do you take a while to switch round the bulbs?

I love the illusion created by the adde bit of wire - great!
 

steirny

Member
Simple pcb etching

I found that floating your pcb on the surface tension of ferric chloride is very effective. All you need is a shallow tray of ferric chloride in a sink of hot water to warm it. Use a bit of self adhesive tape on the componenet side as a handle. Carefully lower the board onto the solution one corner first to prevent trapping air underneath.

Agitate after a couple of minutes, being careful not to sink it. After a few minutes you can see through the board as it etches. Lift up with the handle occassionally for a better look.

Very simple, no fancy do-dads necessary.
 

alpacaman

Member
That is brilliant, alpacaman, although with my one, it is easy to get the ten second reset time my unscrewing bulbs. How long is your reset, and do you take a while to switch round the bulbs?

I love the illusion created by the adde bit of wire - great!
I did cut the 10 second reset time to about 7. I also added a routine where if I leave all the lights on for about 5 seconds the switches will only operate the light directly across from them. This lets you hand the board to someone else to see if they have the magic touch - of course they don't. Right now you have to re-cycle power to start the magic back up again. I've had a lot of fun at restaurants with it.
 

Andrew Cowan

Senior Member
I did cut the 10 second reset time to about 7. I also added a routine where if I leave all the lights on for about 5 seconds the switches will only operate the light directly across from them. This lets you hand the board to someone else to see if they have the magic touch - of course they don't. Right now you have to re-cycle power to start the magic back up again. I've had a lot of fun at restaurants with it.
Did you use technical's code, or did you write your own? I would be interested to see the part of the code that does the on bit - I find that the only problem with mine is that as soon as you hand it across, they work out how it works.

Changing the delay to 7 is not a bad idea either - I have had a couple of annoying moments when it doesn't work.

Andrew
 

hippy

Senior Member
Not sure on the exact code but the best way is to add another timeout which is always set to say 10 seconds whenever the switches are not all on, counts down when they are. When the timeout hits zero jump to different code which is a forced one to one mapping. The only issue then is resetting for more magic.
 

Andrew Cowan

Senior Member
True, and neat...

Anyway, I have reporgrammed it, changing the off time to 8 seconds, and making it so if all are on for 10 seconds, then each switch only works the opposite bulb.

Thanks!
 

alpacaman

Member
Not sure on the exact code but the best way is to add another timeout which is always set to say 10 seconds whenever the switches are not all on, counts down when they are. When the timeout hits zero jump to different code which is a forced one to one mapping. The only issue then is resetting for more magic.
I haven't tried it yet, but I was thinking of doing another all lights on timer to turn the magic back on. As it stands now you have to reset the power.
 

hippy

Senior Member
The trouble with any auto-return-to-magic-land is that you never want that to happen while the audience are playing with it and you can bet that if you've had a good audience it will be doing a long journey with people pausing over it while everyone proclaims they can pull the sword out the stone.

This is quite unique as a prop goes in that the Real McCoy can be handed over to the audience.

Another approach could be to claim the audince have un-magiced the batteries, replace them with some others and a suitable shazzam incantation. Not sure how many times that could be pulled off though without it raising suspicion. You also wouldn't want the batteries to be easy to remove because an inquisitive audience will remove them.

The real challenge here is social engineering rather than electronic.
 

Andrew Cowan

Senior Member
I like the idea of spoiling the magic. However, a problem with both mine and alpacaman's is that by accessing the batteries, the circuit board becomes visable.

Alpacaman - can you take a photo of your PCB? I would be interested to see how you got it to fit in the battery box.
 

alpacaman

Member
I like the idea of spoiling the magic. However, a problem with both mine and alpacaman's is that by accessing the batteries, the circuit board becomes visable.

Alpacaman - can you take a photo of your PCB? I would be interested to see how you got it to fit in the battery box.
Sorry for the blurry picture. But, as you can see, I didn't use a circuit board. I used a wire-wrap IC socket and soldered everytning off the socket's legs. Another part of the illusion of no circuit board is cutting a hole in the cover of the battery box - exposing the batteries (see picture in previous post).
 

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alpacaman

Member
The trouble with any auto-return-to-magic-land is that you never want that to happen while the audience are playing with it and you can bet that if you've had a good audience it will be doing a long journey with people pausing over it while everyone proclaims they can pull the sword out the stone.

This is quite unique as a prop goes in that the Real McCoy can be handed over to the audience.

Another approach could be to claim the audince have un-magiced the batteries, replace them with some others and a suitable shazzam incantation. Not sure how many times that could be pulled off though without it raising suspicion. You also wouldn't want the batteries to be easy to remove because an inquisitive audience will remove them.

The real challenge here is social engineering rather than electronic.
I handed it to a lady once, with the magic was turned off, and I exclaimed that she had broken the magic and I pretended to be upset. Worried, she asked if I'd be able to fix it. It's a lot of fun.
 

Andrew Cowan

Senior Member
Could you? :)

It's great fun - even with the magic on, if you hand it to a person, they usually can't work out how it works.

Andrew

Edit:

On the subject of blury pictures, can someone give me/us some tips on taking pictures of circuit boards? My photos are nearly always rubbish. It does help using optical zoom and standing back, but still...
 

eclectic

Moderator
Andrew.

Two quick tips.

1. Use a tripod / firm support / Gorillapod.

2. Got a scanner? They work well, even for some 3D objects.

e.

ps. Gorillapod is a real product. They're excellent!
 

boriz

Senior Member
(Assuming autofocus digital camera)

DON’T use the flash. Zoom all the way out. Set your camera to macro and use a bright light. Most macro settings will cope with things as close as 10cm. Your camera should tell you if it is focused or not before you take the picture. If it can’t focus, add more light or move back a bit. It should also tell you the calculated shutter speed. If the shutter is less than about 1/60th of a second you should be fine, otherwise you probably need more light. (Note: 1/90th of a second is less than 1/60th)

With a tripod and remote shutter release (or self timer), you can use long exposures in low light. The scanner idea is great. Wanna see a scan of my face?
 

eclectic

Moderator
"The scanner idea is great. Wanna see a scan of my face? "

No Boriz.

Send a scan of a circuit board instead.

e. (ugly beyond belief)
 

Pichucker

New Member
Dear All,

Well, I have finally managed to make my second version of this amazing magic trick. This time I have introduced the concept of "The Magic Knot of Doom". The banter goes along the line of ... "I had a bit of trouble building this circuit and couldn't untangle the wires. I then discovered that the knot actually knows what each user is thinking. Amazing discovery etc etc ...".

I used various sheets of laminated wood. The perception is that it is simply a piece of scrap wood (witha hole right through the middle) with the "fake circuit" clearly visible on the surface. It actually fooled over 40 people last weeked at a family gathering. Not one asked if there was another circuit inside. Most thought there was something hidden on the knot itself or in the battery box.

The globes are the LEDs mentioned earlier in this thread. The only issue is that the are all clear until switched on, so I had to paint the actual colours around the rim. I also used the same colours on magnetic discs, to use as colour indicators which stick to the switches.

Enjoy,
PiChucker
 

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