Monday, September 22, 2014

Adding a uart interface a cheap rfid usb reader 125khz

I got the idea from this video. Seemed pretty simple, and all the rights for this idea goes to the author of the video, I just posted the process.

Open the case, 4 screws.
And this is the reader bare naked.

Locate the UART pin headers.
 The four holes looks like a 5v, gnd, rx, tx pins!!

Solder some wires.

Test it out using a uart-ttl adapter.

Wednesday, September 17, 2014

Struggling with Wireless Charging for Iphone 4s

Yes, Iphone wireless charging inside iphone 4s, no big cover with the circuits.

I got motivated with this video:

Looks really cool and pretty convenient. So After watching this video, I got to shop some items: (all from amazon)

  • Back Cover to strip and fit the wireless receaver. Cover @ Amazon
  • Charge Port, since I might not get it right the first time and would want to break the original one. Charger Port @ Amazon
  • Wireless Charger: Complete kit (Mat and phone kit, it was for a blackberry but the output is the same, and it was dirty cheap). Wireless charger @ Amazon
Also started to investigate about the Iphone port, as to know what pins carry VCC and GND. Thank god to 

According to this video you should use 4 cables... my adaptor only has 2.

  1. Strip down the reciever and get the board clear out with no conectors, just the cables.
  2. Strip down a back cover, to have the reciever fit in, since its pretty slim wont take to much space.
    1. Strip down the parts into layers, theres the outter metalic layer, then theres a plastic layer, and the a metal covering from the inside. All layers are double-side-tape stucked togheter, that means, heat guns/blow dryers can help.
    2. Cut into the the middle plastic layer to fit the reciever (sorry I didnt take any pictures here)
After a few months working:
I must say, it a really difficult making it work. I totalled my battery trying to make it work.

Making it all fit inside the phone, is a cool idea but.... really hard to do it.

Also the wiring into the charging port.....its really small and precise... thank for I bought a replacement, and didn't broke mine. But also its really hard.

Greenbot - Hydroponics system


- yes, I couldnt come up with something better. 

I used the idea posted which seemed simple and nice, for building the whole hydroponic system (breeding seeds its another whole topic, google for it). In order to keep the water flowing into my system, I also fabricated this circuit from electronics-lab, basically this circuits makes a simple one-position switch, works as a "one click: its on" "one more click, its off" circuit, since I was going to use a simple water pump, the cheap ones used in feng-shui ponds, to recirculate the water into the system. 3Dponics uses a airpump (used is fish ponds).

List of matterials:

Plastic 1.5lts bottles
5v power source
on/of switch circuit
Housing for the circuits
Water pump
3dPonics printed items
Extra materials such as: electronical, soldering tools,  power sockets, paint, materials for keeping your plans in the system (rocks, coconut shadings, etc)

First: Building the Toggle ON / OFF Switch

Please visit the electronics-lab page, is has a TON of OPSH circuits. This one is pretty simple, the circuit's pcb is there to download. I used a 5v activated relay, and a arcade button like switch (This one came with a light inside the button, as to tell when its on and when it is off).

Its a simple relay toggle switch, using a "one position" switch

I used an arcade button, with lighting on it, as to know when its on and when its off. Pretty straight forward. 2 Cables are used for switching, and two as power supply for the led inside the button. The led has to be wired to the on/off toggle switch relay.

No major problems building this circuit, and it works perfect, make sure to isolate and my choice I used an insolator spray on the pcb side just in case.

Second: power supply

Either you can build you own one, or.... reutilize something. My choice was to use and old cellphone wall charger, it outputted 5v, so one problem out.
I scrapped a 5v blackberry wall charger for this. Reutilising something at home its always good.

Heres the basic wiring for power supply to switch circuit.

Third: hydroponics building.

First of all your need some seeds, I germited mine using a device that makes them grow with moisture, you just need to leave it with some sort of heating source, and the rest its time.
 These are my chilli seeds sprouting. You can easily moist a kleenex and leave the seeds in a tupperware container on a  dark place, or sitting up your router as to have some heat below and will work as fine.
 I hanged mine!!!
 This is my soil: mixture of rocks and wood chips... since chilli plant tends to get big and heavy they need a way to stay in ground.

The is fashionable and very nice solution, but if you want to keep it simple and cheap, you dont need this part. Bottles are easy to find, and you can use the bottle cap with a hole to drip to the next one.
The top irrigator, can also be made out of something else.

The idea from 3dPonics is great: a vertical hanging hydroponics system, looks great, and (I am hoping) it will work fine. It can also be done indoors.

I also made my contribution for a wall hanger

Monday, January 27, 2014

Designing an RFID antenna - part 1

Designing an RFID antenna:

Basically I am motivated to replace the antenna on this RFID reader. The reader is really cheap, and fits my porpoise, its recognized as a USB keyboard.

My Idea is to build a new antenna that can be fitted into a PVC tube and have a usb "reading rod".

Hackaday has provided me with some information about this, but nothing useful about antenna modding.

Thanks a friend (Chris) I manage to get some technical documents (such as this,  this, this) about this matter, some turned to be really useful and cover basic subject (like Magnetism, Faraday's Law, Mutual induction) it really help me understand more about RFID, it sure brought me memories when I was in college, but could not find any decisive information on how to shape a new antenna.

I know antenna shapes and geometry are dependent on: Frequency (125 Khz in this case) and range of reading (of the tags) and number of turns. Of course many other items, but they are purely derivative from the two I mentioned first.

So I disassembled my rfid reader:

Up to here all done, simple building, now I will desolder the coil antenna, saving it in case of reusing it or take it as a model.

Desoldering was easy, two points, done! You can see below the antenna saved for future.

Now the best part, with 20 meters of copper wire I am planning to do some coils, in order to check which confirations works best.

Three basic squares using push pins, will serve two make the coils and test them.

I have 3 configurations to test:
a)50mm x 60mm
b)40mm x 50mm
c)35mm x 120mm

Tune in for future results!