Category Archives: Tools and Hacks

Fixing my TV remote control

My TV remote control became less and less responsive. Some buttons stopped working altogether while others responded only when pressed very hard or wiggled around in their socket. This situation became truly inconvenient until I decided to buy a new remote control. However, just before going to the store I decided to open the remote control and see if I can fix it.

I found very quickly that the remote control itself work perfectly – when I used a screw to shorten its contacts it responded perfectly. I didn’t even have to check if it emits IR light because this model has an LED that flashes every time a button is pressed. I realised that the contacts at the other end of the buttons are worn out. So I decided to fix them by gluing small caps of aluminium foil onto them.

Luckily this model had a plastic frame with holes for the button, so I placed aluminium foil on the frame and punched nice round caps by pressing the button.IMG_5025

 

I then glued the caps to the buttons with a wee bit of glue to get this:

Fixed remote control

And now the remote control works perfectly except for the volume up/down buttons.

My work bench power supply

I am going to need a power supply for my upcoming product development work. I decided to make one from an old ATX power supply – I have lots of them because one of my queer hobbies is to salvage old computers that people dump in the garbage and take them apart. So I have many old power supplies, and incidentally, here is my collection of old CPUs:

CPU Collection

So I read some tutorials like this one, went to the one and only electronics store in Jerusalem and bought some stuff for about $11:

Parts for converting an ATX power supply

I also used some stuff that I had at home: LEDs, a SPDT switch and some heat shrink.

Stuff I had at home

The first step is to test if the power supply works at all. One possible method is to test if it outputs a standby voltage (called +5VSB). This signal is used by a PC motherboard for functions such as “wake up on LAN” and other stuff it has to do when the PC is turned off. The standby cable is purple, so if I measure the voltage between the purple cable and one of the black cables I should see 5V. As you can see in the next photo, the power supply seems to be ok.

Testing the standby voltage

The next step is planning. I decided to install two LEDs. One to indicate that the power supply is  connected to the mains and the second to indicate that the power supply is on. The power supply will be turned on with a switch. I also decided to provide the following voltages:

  • Ground
  • +5V
  • +12V
  • -12V

These voltages will be useful for various purposes, including for charging my LiPo batteries where the charger input voltage is 11-18V. I decided not to use the 3.3V line.

I cut a piece of paper to the size of the side of the power supply and drew all the connectors.

Connector plan

I started with soldering the LEDs to the purple (+5VSB) and the grey line (Power OK). I soldered a 330 Ohm resistor to the other leg and connected to resistor to a black (ground) line.

LEDs

I connected the switch between the green line (Power on) and one of the black (ground) lines.

Power switch

I connected a load resistor – 10 Ohm 10 Watt – between one of the +5V lines (red) and ground. The purpose of the load resistor is to maintain a load on the power supply because the power supply shuts down if there is no load. I spread a small amount of heat sink to the back of the power resistor and attached it to the ventilated part of the power supply case.

Load resistor

The I grouped the lines by color – black (ground) , red (+5V)  and yellow (+12V). I folded the orange lines (+3.3V) and secured them with a cable tie. I connected the black, red and yellow cables together and into a connector.

Output lines

The additional voltage of -12V is provided on a singe blue line that can be seen at the bottom of the photo above.

I decided to install a 1A fuse on each voltage line. I’m not totally sure it is necessary because these power supplies are protected, but it seemed to be a good idea. I will have to change the 1A fuse to a higher current one when I will start to use the power supply to power my LiPo charger – I still didn’t check the current requirements for the charger, but its display shows 4.5A when it is charging.

Fuse

I covered each fuse in a wide heat shrink sleeve.

The next challenge was to drill the holes in the cover. I tried various drill bits and various ways to hold the cover in place until I finally found this to work – holding a piece of wood in the clamp, placing the power supply cover over it and drilling with my power drill.

Drilling Holes

I inserted the binding posts and all the other components, soldered the wires and drew two nice labels.

Labels

I closed the power supply and started testing. All seemed to be ok. The SB LED came on when I connected the power supply to the mains. The Power LED came on when I flipped the switch. The voltage between GND and -12V and between GND and +5V was ok, but there was no voltage between the +12V and GND. I also noticed that there was a spark when I touched the power supply cover to the body and the +12V fuse was burned. I burned another fuse before I realised that there is a short circuit.

It took me some time to understand that I bought two different types of binding posts. One type had a plastic sleeve that went through the hole. The other type had a narrow metal connector. This connector touched the cover and was shortening.

The solution was to cover the metal connected with a heat shrink tube as can be seen in the next photo (the one on top is covered in green heat shrink)

Covering the binding post connector

I had to enlarge the hole in the power supply cover and drill through the red plastic connectors.

When I assembled the power supply again it worked perfectly.

 

Fixing a broken HJ-450 arm

As I reported in a previous post (an expensive evening), I broke the arm of Misha’s HJ-450 frame.

I decided to glue it back together with epoxy glue. I don’t remember the brand of the glue which I use, but here is a photo:

Epoxy glue

Epoxy glue

I covered the broken edges in a large amount of glue and let it dry for a day:

Glued HJ-450 arm

Glued HJ-450 arm

And … very surprisingly … it held out so far in about 20 landings, some of them not very gentle.

Repairing cracked propellors

Nylon propellors crack easily. Even light collisions with the ground will crack them. However. I also found that they can be fixed by taping them with transparent tape as shown in the photo. I don’t feel any adverse effect of this fix on the way the quadcopter flies.

A cracked propellor fixed by transparent tape

A cracked propellor fixed by transparent tape

 

 

iMax B6 – Connection Break fix

One day my loyal fake iMax B6 charger stopped working. Instead of beginning to charge it beeped ferociously and showed this message on the display:

iMax B6 Connection Break

Connection Break

I unscrewed the 8 screws on the sides of the box and opened the charger. At first I noticed that it was wet inside. There were traces of water and the screws connecting the PCB to the bottom plate were rusty! I marked them in the image below.

iMax B6 Corrosion

I didn’t know how it became so wet but I figured it must have stood near an open window while it was raining outside.

Except for the rusty screws everything seemed to be ok and the display was working fine only it wasn’t charging, so at first I couldn’t find the problem. But then a friend of mine saw that the left resistor at the bottom right side looked burned, as you can see in the next photo.

iMax B6 burned fuse

To verify that this is the problem we measured the resistance of the resistor and found it is very high (we couldn’t tell what it should be because the color stripes lost their original colors). We figured that it couldn’t get so hot and burn if the resistance was meant to be so high.

My friend explained that this resistor is probably acting as a fuse. So I went to my favourite store in Belfast (Northern Ireland) – Maplin Electronics and bought an assortment of low resistance resistors for about 4 pounds (I bought two of each).

iMax B6 fuses

I soldered the 3W resistor in place of the burned one:

iMax B6 Fixed 3

And here is a photo from the top. You can also see in this photo that the charger is charging again at 3.9A.

iMax B6 Fixed

I just hope that the resistor on the right will not burn since there in no place for an additional resistor of the size that I bought …