DIY Airsoft Chronometer/ Chronograph, PC based (Part 4 - Modification)

Just did 2 experiment:
1) Use 2 pairs of IR diode at exit site
easier to catch the exit signal , especially for faster BB > 500fps

2) Use shorter travel ~10cm
Accuracy / consistency of velocity can be kept within 2-3% deviation. Shorter tube results in easier to record the exit signal. The compromise is the time interval becomes shorter and needs more careful selection of the interval.
Audacity is set at 100k Hz sample rate with 16/24 bit (do not use floating as the signal will be lost during higher magnification of time)
Mic gain in Audacity needs to be set at ~90%

DIY Airsoft Chronometer/ Chronograph, PC based (Part 2- Construction)

Circuit diagram. Reverse polarity of the diode will not burnt the diode as the reverse voltage is not high enough to damage it. Make sure your mic input support stereo input. Most P4 or above motherboard has stereo mic.
IR diode is quite resistant to ambient light. U may cover the receiver diode if U found too much noise. Make sure all connection is solder well as small vibration may produce noise in the wave capture in Audacity. Get the orientation of which one is the entry reciever diode end, by testing each channel in the Audacity tracing.

IR sender diode connect in parallel with a battery source. The specified nominal voltage of my 5mm IR diode is 1.7V at 20-200mA. So I use 3V lithium battery with a voltage drop resistor. So 10-100 Ohm 0.5W resistor is ok. Note the polarity of the diode. The smaller metal piece inside the diode is to be connected to the battery positive.

For the IR recevier diode, one of the pin of the entry and exit diode is connected to the stereo plug middle and tip segment respectively (provide 2 channel information . The ground (base of the stereo plug) is connected to the other pin of each diode.

I check the IR sender by using my Sony DV camera. One should see the IR sender diode is lit on.

The IR receiver diode can be checked by using any TV/HiFi/DVD remote controller. One can see the IR spike on the Audacity software.

For small velocity gun, the tracing is easy to be capture. For higher velocity gun, a single exit diode may not be able to capture the signal in just 1 shot, as the BB may pass the exit diode on sideway. U can enhance this limitation by adding more parallel IR receiver diode in the exit end - a curtain of IR that will not miss the BB.

Audacity Software setting .... (to be cont)

DIY Airsoft Chronometer, PC based (Part 3-Result)

This Entry and exit signal with BB firing from my L96 stock. The mic gain setting on Audacity is around 0.9 . One can see the entry signal with some recoil due to the spring (relative movement of the travel tube as I put it in direct contact with my L39 on firing. Measured speed is 143-149 m/s or 490 fps. Muzzle energy just below 2Joule.

Velocity and Muzzle energy calculated from Excel. My M92 blowback - 0.6-0.7J only. Can only shot through 1 side of a coke can.
The 2 channel signal from Entry diode and Exit diode. Note this is captured from my CO2 pistol , in which the gush of CO2 signal is captured as 2 small spike before the BB pass the 1st diode.
Initial Audacity capture interface, showing testing with 3 shots of BB.

Audacity Interface and setting .........

DIY Airsoft Chronometer, PC based (Part 1)

This method is not invented by me, but I modified it with stereo channel of the mic input. The 2 separate channels make construction easier and more accurate.

Items need:
1) stereo plug x 1
2) 5mm IR photodiode receiver and sender, 2 pairs
3) connecting wires
4) 2cm diameter tube of length 25cm (Diode separation 20cm)
5) PC/notebook with soundcard/ motherboard with stereo mic in
6) Software - Audacity version 1.2.6

Facts:
1) Stereo mic, with 2 channels input enable entry and exit measurement be done separate and reduce noise/ interference.
2) IR photodiode is cheap. Do not use phototransistor (more expensive). Do not use those with metal cap (with internal pulse IC for IR TV remote control )5mm diode is used as the area cover will be bigger. If 3mm diode is chosen, you may have difficulty to catch the BB accurately. Make shoulde you know which diode is receiver as sometimes the purchased receiver diode is darker in colour, while sometimes is sold as clear diode (the one I got).
3) Length of travel tube governs the accuracy of the chronometer. The longer the separation (L) of the entry and exit diode placement, the less critical on the accuracy of time measurement. However, the longer the tube, the higher the chance the BB is shot in an angle , resulting in longer path (negligible) and chance the single exit diode not being crossed. (Then U need more than 1 exit diode , in parallel)
4) Time (t) measurement is done manually by cropping the signal spike between the entry and exit diode, from graph plotted on Audacity.
5) Time measured is translate to velocity (L/t) in fps or m/s, and hence the Muzzle energy can be calculated by 1/2 mv^2 Joule in Excel.
6) Error Tolerance is expected to be 1-5%. The higher the soundcard/ mic sampling frequency (44k to 100k from setting in the Audacity software), the higher the accuracy.

7" Android 2.1 MID/ Tablet Touch Screen Calibration Problem

Most peoploe like me find the sluggish and inprecise resistive touchscreen android a bit annoying. I , myself bought one with a faulty touch screen. This is difficult to detect on purchase as we are new to this OS. The virtual keyboard seems working on purchase, but yet the keys on the left hand side of the virtual keyboard seems unable to be pressed correctly persistently. In fact, if you download an apps like Paintpro, you will then find the touching point is 1cm away from the actual pen tip !
Since I am not to sure if that is my problem of incorrect steps of touch screen calibration, I can only make a decision to go back to the shop and ask for a change.
After testing, I confirmed that mine has a faulty touch screen. The shop exchange a "new one" and I test it with Paintpro app to make sure the touchscreen tracking is perfect. Nevertheless, I got a good one.

After playing with that for another 3 weeks, the same symptom appear again!
Googling, I found 3 posts regarding : 1) resolved by reloading the firmware , 2) faulty touchscreen
Initially it seems 1) is a better option as the screen works normal for the first 3 weeks. May be I load some apps not compatible, may be I root it,.....
I cannot just put this lovely pad into the rubbish bin. Finally , I decide to investigate. I dare to peel off the protective screen and confirm my finding.
The resistive touch screen compose of 3 layers (the cheap one has only 2) and the 4 pins are sealed together with some glue/bond. I find if I press on one of the pin, the touch screen becomes percise again. Likely the fault results from manufacturing problem results in one of the pin has poor contact between the 2 layers.

Then I think how to make a good contact for the pin in the upper and bottom layer as they is no point of soldering.

I repair it by using a soldering gun of low Watt and once it reach the desired temp., I switch off the soldering gun. Then hold it firmly and press on the plastic on the side of the pin. It works like magic and the touchscreen revive again.

Steps in repairing your touchscreen:
1) Confirm you can the same problem. The left part of the virtual keyboard does not work properly.The keys like a ,s,w,e cannot be pressed with one touch, it just wander (The reason is that the loss contact add additional resistance to the reading.
2) Try and press/hold on the touchscreen lower left corner,measuring 3.8 to 4.8cm from the left lowest viewable LCD corner. (refer to the photo below)
3) If this cure your touchscreen problem, you can follow as below
4) Peeled off the top screen. This is the most difficult and most destructive part. It may be irreversible!
5) Confirm which oin is loosen but pressing on the pin individually.
6) Apply warm solder to reglue the loose pin.


The LCD is removed.
The 4 pin of the resistive touchscreen.

Use solder gun of low temp and press the side of the pin.

****The soldering method is replaced with silver metal conductive paint, which works easier and safer.

支援Full HD 3D立體影像 LG W2363D-PF 16:9 LCD顯示器 - 電腦領域 HKEPC Hardware - 全港 No.1 PC網站

支援Full HD 3D立體影像 LG W2363D-PF 16:9 LCD顯示器 - 電腦領域 HKEPC Hardware - 全港 No.1 PC網站

Rooting Android HSG X5A Tablet

Steps
A) Install Eclair android USB driver in PC
1) Power on Android Table and wait till boot finish
2) Make sure X5A has USB debugging mode enabled
3) Connect Androdi tablet to PC via USB
4) Install X5A USB Eclair driver, when prompt for driver
5) In PC tray, you should see ANdroid composite ADB Interface
6) Reboot PC

B) In PC , enter ADB mode
1) Run > cmd> adb

My first 7" Android Tablet

7" size just fit into pocket.

The soul of the tablet : 4G NAND flash memory, 64Mx2 = 128M ram ~horrible!

LCD cable

Unsolder are for addition 4G nand.

1800mA 2cell 7.6V lipo

WiFi antenna on the right top.

Model : HSG X5A

Spec: Telechip 8902, 4G nand, 256M ram

Firmware: 2.1 update

Repair Canon EF lens Err99

The cable is now secure with tape to avoid future pulling and fracturing.

The iris mount has the cable exit area "rounded" to remove the right angle on the lip.

Site of fracture as from the small impression on it. The pinhole is puncture to confirm location of fracture.

My Canon EF lens showed this well known Err99 while I was on my long trip to Europe. That was desperate as the problem worsen progressively. Eventually, the camera stops working whenever the lens is zoomed and is fired.

There are lots of reason for Err99, including ring contact, jammed shutter, jammed iris (aperture)....

After returned to my home country, the lens was disassembled. The iris was tested and they seems to have no mechanism binding. The iris works intermittently. Bingo, that should be the broken cable. The cable is visually normal ....hey..except where it exit from the iris mount..there is a impression caused by pulling the cable against the iris housing. Cannon is stupid to allow this happen as the impression cause the thin copper to fracture. Mine counts only around 4,800 shots in 4 years.

Since I got no replacement cable on hand. I decided to confirm the fracture and solder it myself.

Hairpin connectded ohm-meter confirmed the fracture. After careful sanding and solder, the lens now works flawlessly.

Repairing Euron-320 HDTV VCR Power supply.

The replace blown capacitors with dots on it.

Euron HDTV VCR broken down after 1.5 year usage. All instrument light does not lit up. Some ticking noise on power up. Likely somehow of short circuit. On opening up the case. 3 capacitors will blown. With the tanned marking on the circuit board, likely due to overheat , caused by poor design (as the HD still spins and the heat can be felt from the ventilation slot on standby mode).

After changing the capacitors, the circuit board can still not power up. The small tickling noise can still be heard. Likely the short circuit has not yet found out. On removeing the power supply to the harddisk. Bingo! the unit can now be powered up normally.

With ohnmeter checking, the Zener diode (Someone said not zener, ..I forgot ) guarding the voltage input is burnt as well, causing a short circuit. The diode is removed and the unit works nicely...at least for antoehr 4 months.

Now the harddisk list everthing in it. Um....I forgot to check the ventilation fan.. a small , low power fan rated 0.16A and 5V ~1W. I was so stupid that I miss the non-spinning fan. I replaced th fan and it still does not spin and I suspect the old fan is stuck by dust and burnt the supplying transistor as well (some sort of temp. driven fan).

Eventually, I replace with another old 320G harddisk and plug a 3.3V computer fan (for video card) instead.

Hope it works for another 2 years...

ChangeSun 90mm motor fan unit

Motor fan unit using outrunner 1900kv. Running at 6s with amp drawn 70A, the thrust is over 2.6kg. Almost 1.6g/W in benchtesting. My F18 now make a speed record of 180 km/hr.

Quadtwirl gyrotor revived !

My old quadtwirl is revived after its maiden 2 years ago. The torsional weakness is now solve with a piece of 1cmx 1cm balsa running along the fuselage.

Motor now upgraded from 100W to 250W outrunner that runs at 3s/ 20A with a 11x4.7 propeller. THe elevator will be mixed as Delta to provide more roll control. If I were to strengten the rotor, I would insert CF rod + tapes need the rotor blade root.

Converting 220V Hot glue gun to 12V

The heating element : Nicrome wire pressed to the contact slab (solder will melt ! ), the heating resistor 3.6K @220V, which generate rather constant temperature, and the insulating wrap.

These will be replaced by a 2-5W 8 Ohm resistor powered by 2-3s lipo.

SAPAC F16 with 70mm EDF

Now redo the power system with 70mm EDF at 700W. EDF unit from OK Model Tahmazo 3600kv inrunner. Speed now getting close to satisfaction. Needs to reduce the exit nozzle to get extra speed.

F18 90mm Nose strut

The shock absorbing strut works perfectly and one can actually see the nose sinks as the plane lands at nose high angle.

Much lighter that the stock retract and easier to the retract servo.

Bae Hawk shortened nose gear

Shortening the front nose gear makes her never bouncing on landing.

The wire needs some dremel to lock the control arm in position. Now she lands like sticking a magnet !

SAPAC 70mm EDF revive

Very agile and predictabel control F16. Recently upgraded from 400W EDF to 800W. The performance is excellent.

Lightex film is ironed onto the wing, to reduce drag. Lightex on foamy is suprisingly good in reducing drag.

With OK Model inrunner EDF, this F16 flies like composite model.

Eflite Haw - Test flight with Flap modification

The flap is added to slow down the plane on descend.

Smart looking nose strut.

The A4 Sky Hawk is much faster and needs extra attention to fly.

DX7 Switching 3.3V power supply

DIY a 3.3V switching power supply from a 12V to 5V USB car adapter. My DX7 can now run 40% more air time.

Eflite Hawk Flap Modification

Changsun nose strut with "shock absorbing" spring.

This Hawk flies so nice but needs lots of attention when landing. The relative high speed on landing also makes her bouncing. How nice to add flap to slow her down and avoid stall. Simply adding reflex does not make a good solution for perfect landing.

The flap modification is pretty straight forward by cutting along the aileron to the wing root. A servo can be easily attached to the fuselage and a link control.

OK Model A4 SkyHawk Modification

The fastest model of this class with small wing area and high wingloading.

The relatively easy to stall on banking turn is partly explained by the high pressure at wing bottom is stolen into the cheating hole under the fuselage. Therefore, transparent sheet was added to act as guard to prevent high pressure air sucked into the EDF.

Test flight confirmed no easy stall on high bank angle turn, which happens easily on high bank angle turn from downwind to headwind direction.

She is now back to service and flying experience gives more fun than worry.