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BOB'S GADGET CORNER

 

Useful and not that expensive, items or services that you may like for your hobby.

 

Where suppliers are named, these are not a specific recommendation, it is up to you where you purchase, as usually there are other suppliers selling the same item, and at varying prices.

 

It has been a long time since I had anything interesting to put here, however here is something that has taken my interest.

 


Here is a low cost way of getting a 3 in 1 out composite video switch, using 2 small modules.

 


As usual from Ebay, you need at least 1 of these 5.8G 3 Switcher Channel Video Module 3 way Video Switch Unit for FPV Camera around 3.60, (left picture), and a Servo tester around 2.00 or so ! (Right picture)

 


The Video Module.

 

The single row of 3 pins on one end are for Ground, 5V and Servo signal in, DO NOT CONNECT HIGHER THAN 5 VOLTS TO THIS END. Note that the 5volts is not passed to the end with the multiple pins.

 

On the other end are 2 rows of 6 pins (VIDEO) IN1, IN2, IN3 AND (VIDEO) OUT1, each set of 3 pins has Ground, Positive, and Signal. The Signal is the composite video signal, not to be confused with the Servo Signal, ignore the + pin.

 

For the cost, the performance of the switcher is quite reasonable, I have noted that with 3 inputs, there seems to be what looks like interference on channel 2, random white dots in a band, however this may just be the way my wiring is, so I will, when I get time, have a closer look. As there is no circuit diagram available, it could be that 75R might be needed on the inputs.

 

The Servo Module.

 

The OUT pins should be connected to the corresponding pins on the single 3 pin connector of the video module.

 

On the IN connector just connect 5V to the + and - pins, no connection is needed to the S pin.

 

Basically the servo controller sends a short pulse every 20 milliseconds or so, the control knob varies the length of this pulse from around .9ms to 2.1ms  when the pulse is around the 1 ms video 1 is on, a pulse around 1.5 ms and video 2 is on, a pulse around 2100 ms and video 3 is on.

 

 

 

Notes.

Use  screened cable for all the video/audio, as you will get crosstalk on unscreened cable.

 

I have tested the Video module and it can pass audio, so if you have 2 of these video modules, you can switch your audio as well, the Servo tester has duplicate pins on the OUT side, or make a "Y" cable up.

 

Alternative to The Servo Module.

 

Use a microprocessor to do the switching,  available on Ebay for around 5.50 or less, search for Pic12f675 Learning Board Breadboard. (Does not come with ready made code for this application)

 

I have coded and programmed one of these and it works well, the jumpers you see on the board can be removed and the connections are made to the 3 single pins on the video module.

 

The 3 push buttons select the video source, and it can be set to cycle through all 3 cameras,  8-10 secs each source.

 

 


Low cost conventional PCB fabrication

 

I have now tested out a far eastern supplier of prototype pcbs at reasonable prices !

 

Various  sizes are on  offer, I am having a 10cm x 10cm double sided board with all the goodies made.

 

The offer is 10 boards for $19.90 plus just over $10 dollars for registered airmail. I do not think there will be import taxes.

 

On this board area I have managed to fill it with 4 different boards, and will cut them myself from the large board, as I have a pcb guillotine.

 

Gerber composite view screen capture manufactured blank pcbs and part built board with pre-made psu.

UPDATE 2nd July 2015

 

I now have the boards, they arrived end of June, and they are fine, I cannot fault the quality, I did get a couple of things a bit tight in fitting, BUT that was my own fault and easily rectified if I get some more done. I also had to re-submit the files as they were initially rejected - The drilling file did not have the drill sizes embedded, so it has taken about 3 weeks in total, the 1st delay was mine, the second delay was the time the Hong Kong post took to send it on to the UK, they X-ray everything to make sure there are no Lithium batteries I believe, once it arrived in UK (Heathrow) it was just 2 days delay.

 

There were no import taxes etc, due to the low cost, but if you have bigger boards and the cost is higher you could well pay duty and vat !, even if that was charged it is still worth the cost.

 

So for just under 20 and because I filled the 10 x 10cm area, I have 10 main Pic boards, 10 relay boards, 10 pic 8 pin micro boards with regulator and 10 without, all in all - very pleased.

 

So here is the website reference Itead PCBs, I have also found another offering virtually the same service, perhaps next time I need boards I will try them, here is the link, Seeedstudio PCBs.

 

For single prototype board then a milled PCB would be fine, (remember no through plated holes so take that into account when you do the design), for boards in quantity, then conventional method is cost effective.

 

Side Note

 

On the board picture above you will see rectangle "OPT PWR BOARD" this is for the PSU (below) without the display, depending on what is needed, a standard regulator or the power board can be fitted.

 

 

 


 

LOW COST ADJUSTABLE POWER SUPPLIES

 

DC-DC 5V/12V/24V 3A Buck Converter Step Down Module LM2596 Power Supply Output

 

I bought mine from lieblingbaby on Ebay, many other suppliers.

 
 

1.07 including postage, quantities available.

 

(Used to replace a board on a solar water feature pump, no problems at all.)

Product Details:
  • LM2596 Step Down Module
  • Condition: New
  • Input: 3v-40v dc,input voltage must be higher than output voltage of 1.5 v. Can't boost
  • Output: 1.5 V-35 V dc voltage continuously adjustable, 3A max
  • Use SANYO solid-state capacitors, 36 u thickness circuit boards, high Q value power inductors
  • Size: 45 x 20 x 14mm
  •  


     

    LED LM2596 DC 4.0~40 to 1.3-37V Voltmeter Buck Step-down Converter Power Module

     

    One with a display, bought from autumn-square on Ebay, many other suppliers

     

    1.88 including postage

  • Input voltage range:4-40VDC
  • Output voltage range:1.25-37DC adjustable
  • Output current:2A Voltmeter range:0 to 40V,error +-0.1V
  • Input reverse polarity protection
  • Built in output short protection function
  • Built in thermal shut down function
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    How about a component tester, micro-controlled and works very well, bought from Ebay for around 10, there are a number of sellers, this was bought from haruyr_kb, it arrived quite quickly and was packed quite well. Search for "Mega328 ESR Meter LCR", be careful when you search as some do not have the graphics display, just normal a character lcd display.

    Features : 
    1,2013 latest M328 version of the software ,more functions.Chip: Atmega328
    2.128*64 big Backlight LCD display,only 2mA when stand by.
    3,Using 9V battery (Not included)
    Test ranges:
    Inductors, capacitors , diodes, dual diode , mos, transistor, SCR , the regulator, LED tube , ESR,
    Resistance,Adjustable potentiometer
    Resistance :0.1 ohm resolution, maximum 50M ohm
    Capacitor :25pf -100,000 uf
    Inductors : 0.01mh-20H
    NEW Function:
    1:Automatic detection of NPN and PNP transistors, n-channel and p-channel MOSFET, diode (including double diode), thyristor, transistor, resistor and capacitor and other components
    2: Automatic test the pin of a component, and display on the LCD
    3:Can detect the transistor, MOSFET protection diode amplification coefficient and the base to determine the emitter transistor forward biased voltage
    4: Measure the gate and gate capacitance of the MOSFET threshold voltage
    5:Use 12864 liquid crystal display with green backlight
    Specifications: For you reference
    1,One -button operation, automatic shutdown .
    2,Only 20nA shutdown current.
    3,Automatically detect NPN, PNP bipolar transistors , N -channel and P -channel MOS FET, JFET , diodes , two diodes, thyristors small power unidirectional and bidirectional thyristor.
    4,Automatic identification components pin arrangement .
    5,Measuring bipolar transistor current amplification factor and base - emitter threshold voltage.
    6,Via the base - emitter threshold voltage and high current amplification factor to identify Darlington transistors.
    7,Can detect bipolar transistors and MOS transistors protection diodes.
    8,Measuring the gate MOS FET threshold voltage and the gate capacitance.
    9,Can simultaneously measure two resistors and resistor symbol is displayed. Displayed on the right with a decimal value of 4 . Resistance symbol on both sides shows the pin number. So you can measure the potentiometer. If the potentiometer wiper is not transferred to an extreme position , we can distinguish the middle and both ends of the pin.
    10,Resistance measurement resolution is 0.1 ohms , 50M ohms can be measured .
    11,Can measure capacitanceCan measure capacitance of 30pF-100mF , resolution 1pF.
    12.2uF more capacitors can simultaneously measure the equivalent series resistance ESR values. The two can be displayed with a decimal value , resolution 0.01 ohms.
    13,Can be in the correct order and the diode symbol display two diodes , and gives the diode forward voltage.
    14.LED is detected as a diode forward voltage higher . Combo of the LED is identified as two diodes.
    15,Eeverse breakdown voltage is less than 4.5V Zener diode can be identified.
    16,Can measure a single diode reverse capacitance. If the bipolar transistor connected to the base and collector or emitter of a pin , it can measure the collector or emitter junction reverse capacitance .
    18 can be obtained with a single measurement rectifier bridge connection.
    Notice: Before measuring capacitance , the capacitor must be discharged , otherwise very likely damage the meter .

     

     

     



     

    24MHz 8CH 8 Channels USB Logic Analyzer

     

    Bought from Ebay, seller 100fys, Cost for this and the test hooks (different supplier) under 12 .

     

     

     

     

     

    A copy of part of a Saleae unit and uses their software !!!

     

     

     

     

    Speedy 24MHz
    Logic samples each channel at up to 24M times per second.

    8 Channels
    Logic has 8 inputs -- it can monitor 8 different digital signals at once.


     

    The software, you download at http://www.saleae.com/downloads

     

    A set of these is useful for the analyser, bought from kingfull-electronic-company.

     

     

    Digital Display USB Power Voltage Current Meter Tester Charger

     Doctor Type 2

     
    Very useful device for monitoring your USB ports and checking the current devices are pulling.
    Bought from emicroplus (Sent via UK postage included  2.15) on Ebay, plenty of other suppliers around with different designs, if you are prepared to wait, can be bought for less than 1.25 from China/Hong Kong.