Hot-Air Rework Station Repairing

Last week, I switched on my hot-air station to do some soldering job. While I was doing other things, I smelled something. I noticed the smell is from hot-air nozzle. I switched off the station and checked that soldering nozzle is melted down due to overheat. Oop! what the hell is going on.

I quickly checked the problem. There is no air flow at the nozzle. But I still heard the air compressor  sound.

Hot air nozzle is melted down

Today, I tear down and find out the problem. My rework station is a cheap china made, LK852D brand. Here is what inside.

Hot Air rework station inside

There are three boards, one step down transformer, one air compressor inside. There is nothing special, the right board is the controller board for hot-air nozzle and air pump controller. The left down side is the soldering gun controller. The left up side is a 7-segments display controller (3 digits display x 2 ).

hot air gun controller

This is hot nozzle controller and air pump controller. There are two Triacs, BTA136 , one for heat gun and one for air pump. There is also one IC, LM324 common opamp. The circuit is very simple. This is just Triac controller like a light dimmer. The Opamp LM324 is used to control Triac  with thermo-couple feedback, somehow comparator circuit like my previous soldering gun repair.

LED Display and Soldering Iron controller

The upper circuit is 7-Segments display and the lower circuit is soldering iron driver. The 7-segment display driver IC is erased label. I don’t brother what’s inside these board for this moment.

The problem is the air compressor. There is no air flow. So, I removed the air pump outside the case and checked this. The controller of pump works well. The output voltage is measured and this can be controlled by the front panel knob. The noisy sound of compressor state that the driver is worked welled.

 

 

So, I open the pump by removing bottom side screw. This is diaphragm pump type. I quickly check that the both side rubber diaphragms are melted, leak  and damaged. Thus, the pump is not working well.

Air pump inside

 

Damaged diaphragms

 

I cannot source locally the replacement part for this pump. But, I saw a guy is using aquarium pump in DIY hot-air gun.  The aquarium pump are also the same principle as the hot-air pump. Luckily,  I have this type of pump in hand. I bought this pump long ago to use with PCB etching tank but never use it. Good, now I have a good reason to use this.

 

Opened the pump from down side, remove original AC cord and connected with driver output wires. This pump has dual output. I combine the two outputs easily to nozzle pipe like that. There is a air flow control switch beside the pump. I simply switch to high position.

Aquarium pump inside

replaced original AC cord and solder two wires

 

Connect air pipes

 

Then sealed the two air output pipes inside the nozzle pipe with hot glue gun.

 

 

Attached the pump inside the case by cable ties.

Then, switched on and test the hot-air flow. It’s work. The hot air is flow out from heat element nozzle again.

 

 

Finally results and  thought,

- The air flow is not strong as original compressor but it still work

- In most soldering case, the pump controller knob is required to set at 3/4 or 4/5 position. The air flow setting adjustment clearance is not so good.

 

 

DIY PICKit-2 Lite

After some years in PIC development, I built and tested DIY programmers. Formerly, I used LPT classic Tratit style programmer. This programmer is very good and stable for most 16F and 18F PIC mid-range series. Later, LPT port is no more option in modern PC and Laptop. I found out serial port programmer and used JDM-2 for a moment. The problem of JDM and it’s style serial port programmer is that they are very buggy with USB-Serial adapter or even in some low power serial port laptop.

Here is my collection of constructed and tested DIY programmers along with my developments. One day, I may be write about these programmers, the good, the best and the urgly .

 

Finally, I considered to use USB programmer and constructed PicKit-2. This is Microchip original successful PIC programmer and compatible with almost all PIC line.

I consider to use Lite version of than original PicKit-2 design. The lite version is a strip down version of original kit-2 because most of original functions are not required for starter and hobbyists.

The main differences between original and lite version are :

- Lite ver don’t use eeprom because they are used only for OTG programming without PC

-Target voltage detection (3.3V and 5V) circuit is removed because most hobbyist stick on only 5V PIC

Since, the first use, I stick all with my PIC development and found that very stable and convenience to use. My design is based on Blueroom-electronics design. The Blueroon website is down now. This is the copy of PicKit-2 lite schematic from Blueroom.

 

I used BC547 and BC557 transistors in my build. For 680uH coil, I used a small filter coil from ATX power supply secondary output rail. Here is my construction.

For those who interested in 3.3 V target, here is modification of Felixls and Suky for 3.3V targets.

http://www.micros-designs.com.ar/pickit2-clone-5v3-3v/

Pickit-2 lite can be used with original Microchip farmware and software without any problem. The resource can be found here.

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023805

 

DIY Old Laptop to All in One PC

I was busy with some tasks between past weeks. Unluckily, one of my development gear, old laptop was not in a good condition since a few weeks ago. It is a PIII laptop with 1GHz CPU and  loaded with my developments tools. I picked it up from disposal since three years ago. When I picked up this, battery was dead, motherboard was not boot, screen lids were broken.  I checked that mother board power supply capacitors leakage and replaced with new capacitors, fixed the screen lids with some epoxy, glues and heat gun. The old laptop was in service at that time. This laptop was manufactured from  infamous brand  Taiwan manufacturer but it’s performance was surprisingly good and stable. Now, it seem end of life again.

I love recycling and reusing things when there is possible. Is that good for environment and also for my pocket?

So, I started a weekend job to recover this hardware. Here is an original photo of this, screen lids and parts of body are broken. Some keys from keyboard are not respond and motherboard was unstable again.

My Idea is to transform this laptop as All in One PC by flipping installing LCD screen over body and making a base+mounting stand my self.

Take apart all parts first. Removed battery, keyboard, mouse pad, up-side cover, floppy drive and CD drive.

Up side cover with speakers, mouse pad.

Removed LCD screen from body.

Took off mother board to clean and to check.

The problem was the same as previous, leakage  capacitors at power supply. Replaced these capacitors and mother board is boot again. This is a common fault symptom of electronics devices especially manufactured about 2000 or cheapo ones.

Started hand-tools jobs.

Prepared down side cover holder. Reinforced with two metal flat sheets.

Finished down side cover with holders. Two L-shape aluminium support ware also installed at the side to fix LCD panel.

Took off LCD panel. I want to flip LCD panel and re-install it over the motherboard part to form like All in One PC. The LCD  connector cable was a little short to do this. So, the cable was took of and straighten and repacked again.

To seat LCD panel over down side cover, I installed L-shape aluminium stands at the back side of LCD cover.

Prepared the base and stand for mounting.

Panel mounting was finished.

The back installation of panel mount.

The first test assembly of down side cover and mount, base.

Re-installed motherboard, hard disk. Old battery, keyboard, Floppy and CD drive ware completely removed.

Speakers were re installed at new place (originally battery place).

First test assembly was finished. All in One style!!!

 

Back side of assembly. L-shape angles are used to attach LCD scree to base. A USB hub is attached and USB WiFi adapter is installed.

I bought a USB keyboard for re-branded PC.

Finally, the oldie classic PIII All in One PC is alive at my workbench. How a happy weekend hacking.

 

 

By the way, this is my last post of 2012.

HAPPY NEW YEAR TO ALL.

DIY Isolation Transformer

After I bought my test gears such oscilloscopes, I noticed that I should have an isolation transformer in my bench. Then, I forgot again with the other projects. One day, after seeing Dave and Todd videos blog about isolation transformer, I started the construction of DIY isolation transformer. For those interests, here is Dave and Todd explained videos. Thanks both.

http://www.eevblog.com/2012/05/18/eevblog-279-how-not-to-blow-up-your-oscilloscope/

http://www.toddfun.com/2011/04/30/isolation_transformers/

Some designed by cascading back to back secondary winding of two transformers (220V||12V<->12V||220V). It also be worked fine but I build my own. One of my buddy’s local transformer manufacturer wound this transformer and give me as present. Thanks buddy again.

It was designed as

• Rating : 1KVA, 220V
• The core  cross sectional area : 60mm x 60mm
• Primary winding & Secondary winding : 300 N, 17SWG

The two winding should be wounded together to avoid turn ratio mismatch.

I found old charger chassis and collected some some required staffs such as sockets, fuse etc.

Seated transformer at chassis base. Prepared face plate, cover hole with plane PCB, installed input and output fuse houses, lamp. And wiring,

I agree with Todd suggestion. This is the schematic from commercial isolation transformer. The output winding NEUTRAL is CONNECTED to main GROUND!!!

http://www.carebase.com/Isolation-transformer-line-conditioner-neutral-ground-bond-EI-core-low-impedance-120V-120vac-600VA-1000VA-1kVA-ILc-600B-1000B.htm

This is the edited diagram as per suggestion. Disconnected secondary winding (NEUTRAL) from main GROUND. Mine has no circuit breaker and surge protection but both input and output fuses.

Final assembly is look like that. A new tool is at my bench.

Note :

- DUT (device under test) should be isolated with transformer rather than oscilloscope.

- BUT, Dave scenario-3… if  DUT power supply is grounded to chassis (main ground), the problem is still existed. Disconnect DUT ground ?? or use with floating power supply?! or with battery?

- Test device such as oscilloscope should not be floated (must be grounded) without special reason.

- Most forum and articles talked about isolating oscilloscope not DUT. If someone know the best practice and pros, cons, let me know.

- Differential probe, usb isolator are also good but cannot still effort.

- I need GFCI outlet at my bench.

UPDATED:

I recently found a post at Keith’s Electronics Blog. There is also original schematic from manufacturer. It isolates even ground pins of each output. Yes, system ground (Chassis ground) is purposely isolated.

- My thought is that isolating system ground has some pro and cons. Sometime we need to isolate for full safety or purposely. In most case, test equipment should be grounded for safety.

Refrubrishing My Isolation Transformer

and schematic from Keith’s Blog

DIY Musical Keyboard in Action

Visitor from DP requested the device in action video. Here are these videos. Sorry for poor quality. I don’t have a video camera and I try to use webcam and laptop to capture this. The first video is tuning with Nexus 7 gStrings app and second one is testing.

Matseng from DP forum said that “So many tone generators.. “. yes it is.

Every musical instrument is basically tone generator. At least 12 tones generators are required for 12 pitches, C,C#…A#,B (ie: 12 freqs) for such devices.
pros of this 4060 design are;

•  required only 12 x 4060 ckts for 84 keys. I only used 48 keys because I have only 48 salvaged keys.
• easy to tune, I need to tune one tone for each octave

If I use other oscillators (without uC), 84 tone generators will be required for 84 keys.
I have to add more effects and control ckts soon.

Contest entries are awesome.

DIY Musical Keyboard

The idea is to design and construct an electronic musical keyboard with some functions, effects etc,. This is my old school project and I remake and modified it. It is fun.

There are many hobbyist’s musical keyboard circuits around the net.  Most design are based on 555 or some oscillator circuits. The limitation of these design are that this circuit generates only one tone at a time. To play a real chord, several keys  are to be pressed at the same time and generate multiple tones at the same times. Ie,. for 12 tones, there will be 12 frequency generators are required. If a keyboard has 48 keys, 48 tone generators are required.

This can be saved by 4060 CMOS logic chip. The 4060 is 14-stage ripple-carry binary counter/divider and oscillator. The internal function block diagram of 4060 from datasheet is as follows. Output Qn is the nth stage of the counter, representing 2^n, for example Q4 is 2^4 = 16 (1/16 of clock frequency) and Q5 is 2^5 = 32 (1/32 of clock frequency).

4060 IC functional block diagram (from TI data sheet)

The frequency of chromatic scale can be learned here.

http://en.wikipedia.org/wiki/Chromatic_scale

http://www.harpsatsang.com/harp_design/data/frequencies.html

There are a relation between the frequencies of octaves scales. The first octave of  C1 (16.3Hz) is half of second octave C2(32.7Hz) and so on. The 4060 IC can divide its clock frequency via Qn outputs. We will need 12 x 4060 tone generators and it will supports 7 octave as maximum (12×7 = 96 tones, bingo).

Thus, the initial design is like that. The design is composed of 12×4060 tone generators, a dsPIC for sound effect and control, an amplifiers.

Musical Keyboard block diagram

The first circuit is 4060 tone generators. The clock frequency can be calculated as f = 1 / (2xPixR2xC1). I plan to use 4 octaves (48 tones) and starting from C3(130Hz) to B6(1975Hz). You can choose what scales are used. For roughly calculation, the adjustable  frequency range of RxC circuit should be covered this selected range. For next expansion,  I prepared for 6 tones outputs in design.

4060 Tone generators circuit

The next circuits are simple 7805 power supply and LM386 audio amplifier. Nothing specials.

7805 5V regulator

LM386 audio amp circuit

The first step is preparing the physical key and PCBs. The keys are salvaging from old toy china made keyboard. Unfortunately  the switches from toy keyboard used matrix keys. So, I made a PCB for switches also.

PCBs,

Prepared switches bar with the original switches dimension.

And next switches assemblies,

And circuits and wiring,

Initial setup is finished.

Tuning the frequency, I used my Nexus 7 and gStrings tuner app .  Thanks the developer for such useful applications. Only one octave is required to tune. Once,the C3, C4 or one of any note is tuned and the rest will be in-tune atomically because of frequency divider.

Finally, after some weekends and many coffees, the first phase design is like this.

The next step:

- You may notice the blank space at the moddle of board. Yes, this is for dsPIC sound effects and control

- I have to make a upside cover also.

Thought:

- The switches are not ease as original keyboard. I have to find more proper solution for final design.

- The LM386 amp is not matched with tones. I notice some distortion in low volume. I will replace with a proper stereo amplifier in next phase. I want the left and right octaves with separated effect and sound output.

For now, it is ready for open 7400 logic competition because it has only discrete logic .

Bus Blaster v2 and gift arrived

last a few weeks ago, I ordered Bus Blaster v2 from Seeed, my favorite open hardware facilitator and supplier. Bus Blaster v2 is an experimental, high-speed JTAG debugger from Dangerous Prototypes. I explorer the world of embedded and this tool will help me a lot.

Luckily, it was a 4th annual birthday of Seed and I also got a Seed T shirt and solar charger shield as special mysterious gift. Thanks to Seeed. Sure, I will make a renewable energy project with this shield.