Electrical Engineering V2

[Waxx]

Hello all, been skimming through this thread and I'm rather humbled by some of the stuff going on here. I'm toying with the idea of a small project but beyond soldering wires, I understand nothing about electrical engineering, so I think you guys will be the ones to ask about this.

Some background on the project: I play airsoft on weekends and occasionally we do objective-based rounds, often times centered around defusing a 'bomb'. I'm pretty handy with making decent-looking props and I offered to make something a little cooler than a spray-painted tissue box wrapped in duct tape. I thought it would be really cool to make something that aesthetically resembled the CS:S C4 weapon, with the keypad and LED readout and all that. My first inclination was to use an LED kitchen timer and unhook the speaker, then rewire it to an alarm siren, but the idea of having a keypad input required to trigger/detrigger the alarm keeps coming back to me.

I spoke to a few friends who recommended looking into arduinos but really, I'm looking for something basic, inexpensive, and if need-be, hacky and unprofessional looking. That said, it does need to be reasonably durable because in all likelihood it will be handled by a bunch of teenage children, thrown around, dropped and kicked about in its lifetime. I feel confident I can build a strong enough outer shell to house these parts without damage, however.

Here are some of the parts I was looking at using:

[url=http://www.amazon.com/Presto-04213-Electronic-Digital-Timer/dp/B001CQG618/ref=sr_1_1?ie=UTF8&qid=1401718304&sr=8-1&keywords=kitchen+timer]Kitchen Timer[/url]

[url=http://www.amazon.com/Honeywell-WAVE-2-Two-Tone-Siren/dp/B0006BCCAE/ref=sr_1_5?ie=UTF8&qid=1401715950&sr=8-5&keywords=siren]Alarm siren[/url]

I see on Amazon there are some very cheap 'home security' keypads that trigger door unlocking mechanisms, [url=http://www.amazon.com/BF-Systems-Home-Security-System/dp/B004TZ155Q/ref=sr_1_29?ie=UTF8&qid=1401716258&sr=8-29&keywords=security+keypad]such as this one.[/url] Is it possible to pick up something like this and through various means wire it to trigger the on/off buttons on the kitchen timer?

Yes, I know how this looks, it's occurred to me throughout the entirety of my consideration of this potential undertaking. Please forgive my ignorance of all things electronic, this is the extent of my understanding of these things. Any information or help you could provide would be very much appreciated.

[Tw34k]

It would be fairly easy to build a replica using an arduino, keypad, speaker, and small lcd screen but due to the way people could potentially over react to a prop and how much trouble someone could get you in for making this sort of replica, It's probably not a project worth pursuing.

"so what are you in for?"

"I made a cardboard bomb prop from a video game some lil old lady thought was real and got me convicted as a suspected terrorist because she had nothing better to do in her boring old life"

"enough chit chat, grab your ankles boy"

[url]https://www.sparkfun.com/products/8653[/url]

[url]https://www.sparkfun.com/products/9393[/url]

[url]https://www.sparkfun.com/products/7950[/url]

[url]https://www.sparkfun.com/products/12640[/url]

In a nutshell my idea was to have the keypad start the timer once you type in the code from the game (7355608 IIRC) the piezo buzzer would be playing the tones from the arduino using the tone library and updating the timer countdown on the lcd until time runs out when it would light up/long beep from buzzer unless you re entered the code before the timer ran out.

Hardware is simple as pie with this, the magic is in the code.

[Waxx]

Oh trust me, that's been on my mind. I'm embarrassed to even ask about it just because of how it looks, but I figured 'what the hell, this thing is so hollywood looking it should be rather obvious to whoever reads it'.

Edit: Those components are quality looking, but I have no idea what to do with an arduino processor or how to program it. Like I said, I have the barest understanding of these things and programming has escaped me every time I've attempted it.

[Tw34k]

[QUOTE=Waxx;44978172]Oh trust me, that's been on my mind. I'm embarrassed to even ask about it just because of how it looks, but I figured 'what the hell, this thing is so hollywood looking it should be rather obvious to whoever reads it'.

Edit: Those components are quality looking, but I have no idea what to do with an arduino processor or how to program it. Like I said, I have the barest understanding of these things and programming has escaped me every time I've attempted it.[/QUOTE]

I ca probably rig up a simplified schematic for the hardware. I'm a shit programmer though so that part would take me a lot of time or require someone else to assist.

I've sort of wanted to build one of these for a while myself just as a desk prop (cs is my most favorite game) I'm just too scared about the possible consequences.

[Waxx]

Wow, yeah, if you'd be willing to try sketching it out for my pea-brain, I'd love to have a look at it. And likewise, if I get it to work, I would not mind talking about building you one for your desk, even a non-electronic one.

[pentium]

What's a good replacement for paper wax capacitors?
I got uh, a lot of them to swap out in a project.
[IMG]http://i11.photobucket.com/albums/a166/ballsandy/CGS_0715.jpg[/IMG]

[LoneWolf_Recon]

Generally speaking, plastic film caps.

[jamie]

Any of you guys in the UK know of a really cheap supplier of stuff?

[Chryseus]

[QUOTE=jamie1130;44995743]Any of you guys in the UK know of a really cheap supplier of stuff?[/QUOTE]

bitbox, CPC or RS if you want good quality and fast delivery.
ebay or DX if you don't mind waiting.

[QUOTE=pentium;44994603]What's a good replacement for paper wax capacitors?[/quote]
Usually film capacitors are the best choice, keep in mind that if the capacitor is used in a tuned network you will
need to retune it after.
Mica caps are usually fine so should be left alone as new ones are very expensive.
[url]http://www.vintage-radio.com/repair-restore-information/valve_capacitors.html[/url]

[Tezzanator92]

Today I was surprised, I got an Arduino ethernet shield (Wiznet W5100) in the post for a project.

I am sending UDP broadcast packets with raw RGB information to display on one of those 32x16 LED Panels. Packing the data into nibbles, two pixels spanning three bytes ([RG][BR][GB]).

I totally did not expect a little Atmega328 to be able to do that, but it seems to be managing 10FPS with ease, I have a little c# program taking pixel data fro my laptop, applying a simple gamma adjustment and blasting it over the network. The result is a component to an LED wall. Didn't think it would be able to handle that.

[HeatPipe]

[QUOTE=Tezzanator92;45001218]Today I was surprised, I got an Arduino ethernet shield (Wiznet W5100) in the post for a project.

I am sending UDP broadcast packets with raw RGB information to display on one of those 32x16 LED Panels. Packing the data into nibbles, two pixels spanning three bytes ([RG][BR][GB]).

I totally did not expect a little Atmega328 to be able to do that, but it seems to be managing 10FPS with ease, I have a little c# program taking pixel data fro my laptop, applying a simple gamma adjustment and blasting it over the network. The result is a component to an LED wall. Didn't think it would be able to handle that.[/QUOTE]

I tried that with AtMega8 but failed...

Wanted to display 8x5x(RGB) (120) leds with BCM modulation via shift registers but failed badly (I think it should have been programmed in assembler.. and also memory was problem, I needed 8 bits per led, which is 120x8 -> 960 bits, and AtMega8 has 1024 bits of memory.. so there would be left 84 bits for program lol...

Now when I think about it, it could actualy work..

[HiddenMyst]

I spent the week figuring out shift registers and making this little test circuit. Next step I think will be learning a PCB design program and sending off to OSH park or something.
[media]http://www.youtube.com/watch?v=vHcfkf6FsI0[/media]
The idea is that the bar graph will be the mouth of the robot plush, with a couple of other LEDs in the eyes and probably a little sound circuit to make some beeps and boops.

[Hng]

Where's a good place to order a raspberry pi that can deliver to ireland?

Modmypi has insane shipping costs (18 euros), and I can't find coupons to lower tha.t

[Chryseus]

[QUOTE=Hng;45009176]Where's a good place to order a raspberry pi that can deliver to ireland?

Modmypi has insane shipping costs (18 euros), and I can't find coupons to lower tha.t[/QUOTE]

Farnell / Element14 maybe ?

[Ddrl46]

Woohoo, won something nice on eBay, a HP 8558B spectrum analyzer up to 1.5 GHz in a HP 182T mainframe.

[img]http://activefrance.com/TechShed/HP8558B%20Spectrum%20Analyser.jpg[/img]
(Not my picture, didn't receive it yet)

[HeatPipe]

[QUOTE=ddrl46;45016031]Woohoo, won something nice on eBay, a HP 8558B spectrum analyzer up to 1.5 GHz in a HP 182T mainframe.

[img]http://activefrance.com/TechShed/HP8558B%20Spectrum%20Analyser.jpg[/img]
(Not my picture, didn't receive it yet)[/QUOTE]

But can it measure CPU clock speed of computer that runs Crysis?

Ok enough with this un-salty joke, thing looks nice!

[Ddrl46]

[QUOTE=HeatPipe;45016576]But can it measure CPU clock speed of computer that runs Crysis?

Ok enough with this un-salty joke, thing looks nice![/QUOTE]

It can with external mixers :v:.

[MatheusMCardoso]

[media]http://www.youtube.com/watch?v=7r9Gmi-WK7I[/media]

modular robotics
[t]http://i10.glitter-graphics.org/pub/459/459480i1wqecqahe.gif[/t]

[TCWilliamson]

Just finished up CADing the replacement part for a broken 8A variac i brought for £3~

[img]http://i.imgur.com/GKFrYNX.png[/img]

[editline]7th June 2014[/editline]

Also need to find a way to fix / replace the brushes
[img]http://i.imgur.com/ThjirjI.jpg[/img]

[Cakebatyr]

Out of interest to those with Arduino Mini Pros, how are you mounting then to your projects? Zip ties?

[Zero-Point]

[QUOTE=Cakebatyr;45030020]Out of interest to those with Arduino Mini Pros, how are you mounting then to your projects? Zip ties?[/QUOTE]

I'll probably do hot-glue with mine.

[DrLuke]

[QUOTE=Amiga OS;45034821]My Commodore VIC 20 has just kicked the bucket, a MOS 6522 chip has blown, its the IO controller for the tape and floppy drive.

I've managed to find a bunch of rockwell manufactured replacements on Alibaba but the listing is quite vague. Where do you guys source older hardware from apart from the usual places like farnell?[/QUOTE]

Ebay is a good source for that.

[Ddrl46]

[QUOTE=Amiga OS;45034993]I've found one from the USA for £5 shipped, I'll be socketing the board in case it pops again, desoldering chips isn't fun.[/QUOTE]

I'd check your power supply before putting a new IC in there, ICs usually don't blow up on their own.

[Ollie]

Hey guys, I've got a problem.
I have an android hooked up to a TSL257-LF light sensitivity sensor.
I'm reading the voltage through an analog pin and converting the reading of the adc to voltage with this formula:

int voltage = (analogRead(5)/1024.0)*5.0;

This gives me a voltage reading, but I'm not sure if it's correct.

The problem: I want to read some sort of lux value, but I can't find any way to relate the voltage to the irradiance.

[URL="http://www.google.fi/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.ams.com%2Feng%2Fcontent%2Fdownload%2F250427%2F976469%2Ffile%2FTSL257S_Datasheet_EN_v1.pdf&ei=ebaYU4veKIe0ywOqkYGwCw&usg=AFQjCNGcy5c-BmTbE2pXAGSw8QZCaRQ0jA&bvm=bv.68693194,d.bGQ&cad=rja"]Here's the datasheet[/URL]

[DrLuke]

[QUOTE=ollie;45074936]Hey guys, I've got a problem.
I have an android hooked up to a TSL257-LF light sensitivity sensor.
I'm reading the voltage through an analog pin and converting the reading of the adc to voltage with this formula:

int voltage = (analogRead(5)/1024.0)*5.0;

This gives me a voltage reading, but I'm not sure if it's correct.

The problem: I want to read some sort of lux value, but I can't find any way to relate the voltage to the irradiance.

[URL="http://www.google.fi/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.ams.com%2Feng%2Fcontent%2Fdownload%2F250427%2F976469%2Ffile%2FTSL257S_Datasheet_EN_v1.pdf&ei=ebaYU4veKIe0ywOqkYGwCw&usg=AFQjCNGcy5c-BmTbE2pXAGSw8QZCaRQ0jA&bvm=bv.68693194,d.bGQ&cad=rja"]Here's the datasheet[/URL][/QUOTE]

You should cast the float to an int, like so:

int voltage = (int)((analogRead(5)/1024.0)*5.0);

[Chryseus]

[img]http://puu.sh/9px1L/b5adc84687.png[/img]

Oscillator time!

[b]Edit:[/b]

[t]http://u.cubeupload.com/Chryseus/s3pQTk.png[/t]
[t]http://u.cubeupload.com/Chryseus/iN5nKn.png[/t]

Works fairly well, only slight problem is I can't get it above 20-25MHz or so since the impedance of the capacitive divider drops too low, I
need some smaller caps like 1pF.
Or I could convert it from a colpitts design to a hartley oscillator and wind some 10uH inductors but it's kinda hard to get a good Q with
inductors compared with caps particularly at high frequencies.

[Hng]

What are some fun things to do with a raspberry pi? What have you guys done?

[HiddenMyst]

I converted my camera to take infrared photos, so I made this neat little IR flashlight thing to go with it:
[t]https://dl.dropboxusercontent.com/u/62766551/P1170441.jpg[/t]
[t]https://dl.dropboxusercontent.com/u/62766551/P1170445.jpg[/t]
[t]https://dl.dropboxusercontent.com/u/62766551/P1170446.jpg[/t]
It's a simple setup with 5 LEDs running parallel on each row and then 5 rows all in series together, all powered by a 9v battery. Never realised how useful stripboard is for making light arrays like this.
If I find somewhere online that has these LEDs at a better price, I'd love to scale this design up to 100 LEDs and maybe make a silvered enclosure to maximise the performance of it.

[LoneWolf_Recon]

[QUOTE=Hng;45100221]What are some fun things to do with a raspberry pi? What have you guys done?[/QUOTE]

HiddenMyst is currently building an all in one keyboard PC using a Pi. A friend of mine is using several for a cluster computing project, and I'm using mine as a file server

[Ddrl46]

Woop, its running after taking apart the stupidly complicated switch assembly and replacing a few wipers in the switches (which wasn't fun)!

[url=http://i.imgur.com/rYd2dYv.jpg][img]http://i.imgur.com/rYd2dYvl.jpg[/img][/url]

[url=http://i.imgur.com/gLGKolK.jpg][img]http://i.imgur.com/gLGKolKl.jpg[/img][/url]