June 10th, 2009

DIY 2.5GHz Counter with AVR

DIY 2.5Ghz counter with AVR

Counters that can go into gigahertz range can be pretty expensive so you might want to consider DIY solution if your measurements are not critical. Of course since we are dealing with extremely high frequency the quality of the build depends highly on your skills. Care must be taken with PCB manufacturing, component placement, screening and shielding, noise sources, etc.

This is a project of a counter built around AT90S8535 microcontroller and it measures both the frequency of the input signal and it’s strength. The values are display on a LCD, the signal strength is shown dBm units and as a bar-graph. Also you can use it with an external 10Mhz clock, in this mode on LCD will be displayed the letter “E”   in the left upper corner and “I” when internal clock is used.

Since AVR microcontrollers have synchronous counter input, the law says the maximum input frequency should not exceed half the clock frequency. Even so 2.5Ghz is way too high for the microcontroller to handle, so a prescaler that divides that frequency to a measurable one is needed. The input impedance of the prescaler is set to 50 ohms, the signal is amplified by 20dB and then fed into a two way splitter. One way goes to the Analog Devices AD8314 log-detector for signal strength measurement.

The other way goes to the first divider, MC12095, set to divide by 2. Putting pin 6 (SW) to ground would set the dividing factor to 4. MC12095 can accept 2.5Ghz input frequency. The output resistor increases output power and keeps impedance at 50 ohms, the parallel 2pF capacitor is for impedance matching. The next divider, SAB6456 can be set to divide by 64 or 256, in our case 64 is used by leaving pin 5 (MC) unconnected.

The divider’s output is then gated with nand gates and reaches a 4020 counter. AVR counter works on 16 bits and with 14 bits from the 4020 we get a 30 bits counter. The source code for the microcontroller is writen in Bascom and you can find it in the link for download. A test is presented with a 500Mhz signal but i was  curious if it can really go far up to 2.5Ghz. Let me know if you build it and test it.

DIY 2.5GHz Counter with AVR: [Link]

June 4th, 2009

4 Digit PIC Counter

4 digit PIC counter

A counter is a very useful tool, i for one could use one when I’m winding coils. These days a counter project caught my attention, because it can be configured for many applications. Basically it’s a 4 digit decimal counter that can go from 0 to 9999 in either direction, can stop when it hits the maximum counting value or can be left in free run.

The maximum counting number can be set by the operator to a desired value, which is stored in the EEPROM of the PIC16F88. This is very helpful, looking at my coil winding example i can set this way the number of windings. You can also set it to count up or down and has an overflow output which can be used to control an external device once the counter reached the preset number, in my case to turn off the winding motor.

The clock input is port B0 of the PIC and can be set to count either rising or falling clock fronts with or without zero suppression. Schematics show a debounce circuit to be used with mechanical contact switches at the clock’s input, which will accept 5V logic only.

The counting is displayed on four 7-segment LEDs and operation mode is shown on other four LEDs. D7 will indicate overflow, D8 Count Hold and D9 and10 will indicate it’s counting up or down. The whole display is multiplexed, more information about that you can find here. There are five push buttons you can use to configure the counter.

Schematics, source code and hex file for PIC as well as detailed explanation of operation can be found in the link.

4 Digit PIC Counter: [Link][Via]

April 19th, 2008

Electronic Hits Counter

Electronicd Hit Counter in action

This is a physical hit counter.It is used to count page-hits on the website instead of using software only.The counter will be connected to rs232 port through a few of electronic components that performs as a counter driver and power supply circuit. The circuit is based on MAX7219 and 7-segment common cathode LED display x 8 digits. MAX7219 is a 8-Digit LED Display Drivers with serial interface which makes it ideal for this project and really easy to implement.

I will sure build one of these for myself, with some minor tweaks, it will look great on my desk 🙂 . I will write about it in a following article so Subscribe by RSS or email to get the news from this blog.

Electronic Hit Counter: [Link]

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