0-99 seconds/minute 2 Digit Timer

I make this micro controller based timer as a part of shooter training Project.we can select and set time for a period of 0 t0 99 seconds or minutes. when the the timer is start.the 2 seven segment display start counting down .when it reach 0 an out put voltage activate buzzer or relay .so any electrical device can be switched on or off after a time delay

¶Microcontroller based design for greater accuracy and control
¶Power supply input 12 VDC 200 mA
¶Two 7 segments Display to display time
¶Single key start and dual key alarm time set function
¶Power and Relay-On LED indicator
¶Terminal connector for connecting power supply input and relay output to the PCB
¶Onboard regulator for regulated supply
¶Crystal resonator based design for better accuracy

there three buttons Up Down and set button

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Ring tester

In my Electronic repair job I found normal multimeter is somewhat limited in certain area. so special tools are needed for saving a lot of time Ring tester is one of this kind .helping me to check small hi Q inductors SMPS transformer, TV Deflection coils ,LOT ,line driver transformer and almost any inductor working on hi frequency.Normal multimeter can only identify a open coil ,but not a shorted windings. I found some commercial available ring tester. but it is not available in local shops of my area.also it seems priced high. So I decided to make a ring tester of my own. Below is the one I successfully made from the junk box components. I found it very useful. and now it is one of my best test tool collection. Two Ic's, few LED's ,one plastic container and few resistors made this wonderful tool. If we test it with primary of SMPS transformer or LOT windings of a good one shows all its LEDs will light. depending on the inductive reactantce the number of LED 's

Transistor numbers and codes

Most transistor markings follow one of these codes: JEDEC, JIS or Pro-Electron. For ICs, look for known numbers (e.g. 741, 4001, 7400) between the prefix and the suffix. Don't confuse it with the date code. ICs typically have two numbers: The part number and the date code. 1. Joint Electron Device Engineering Council (JEDEC) These part numbers take the form: digit, letter, sequential number, [suffix] The letter is always 'N', and the first digit is 1 for diodes, 2 for transistors, 3 for four-leaded devices, and so forth. But 4N and 5N are reserved for opto-couplers. The sequential numbers run from 100 to 9999 and indicate the approximate time the device was first made. If present, a suffix could indicate various things. For example, a 2N2222A is an enhanced version of a 2N2222. It has higher gain, frequency, and voltage ratings. Always check the data sheet. Examples: 1N914 (diode), 2N2222, 2N2222A, 2N904 (transistors). NOTE: When a metal-can version of a JEDEC tra

Short Finder

Today i made this Test instrument using Arduino ..very very usefull in find out shorted electronic components in mainboards.. espcially when lot of ICs sharing same power. if one componet get short the whole track shows 0 resistance when testing with normal multimeter.. its difficult to find which one is the dead rat. Normally we need to take out each suspected component from board and need to test until we got the defective one.. its tedious job and damage the board. Another way inject current to the circuit test the heat.. its not safe. Here is the need of this device. When we trace the power line with this probe.. it gives high pitch audio tone when the probe near the particular shorted component.. It can test micro ohm resistance beyond normal meter range Automatically shut to save battery .if we forget to switch of the tester Auto calibration range. Portable The tester voltage and current safe to testing any components . On board testable.. Happy troubleshooting

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