frequency counter

30 Articles

Making A HP Frequency Counter More Accurate

August 26, 2013 by 38 Comments

[Gerry] built his own high stability timebase add-on for his HP 53131 frequency counter. This project started out after [Gerry] built a rubidium 10 MHz standard for his lab. Upon connecting the standard to the frequency counter for calibration, he found that the HP 53131 had an awful internal oscillator. The official high stability timebase add-on from HP cost about $1000, and he was determined to do better.

Using a second hand OCXO as the oscillator, he designed his own add-on module. OCXO modules pack a crystal oscillator in a thermal chamber. Since temperature fluctuation causes drift in crystal oscillators, an OCXO controls the temperature to keep the frequency constant. They can be bought second hand on eBay for under $30.

The PCB design for the module can accommodate a variety of OCXO modules. It uses a high speed comparator and a high stability 5 volt reference to provide the clock signal to the counter. A DAC is used to calibrate the oscillator. By keeping the same DAC as the original counter, the add-on board can be calibrated using the front panel of the device.

The project is a drop in replacement for HP’s $1000 module for a fraction of the cost. [Gerry]’s write up has all the details you’ll need to build your own.

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Arduino As An Inexpensive Ham Radio Frequency Counter

February 9, 2013 by 8 Comments

[Todd Harrison] really has our number. Like him, we don’t want to spend money when we don’t have to, and hacking our own solutions is a lot more fun anyway. This time around he’s helping out a friend who is a ham radio enthusiast. The friend’s radio didn’t come with a frequency display, and buying the add-on would cost more than the radio did. So [Todd] has set out to build an Arduino frequency counter for a Kenwood TS-520S HF ham radio.

This post (and the video found after the break) doesn’t cover the entire project. It’s rather involved just to make sure that [Todd’s] initial idea is viable so he spends about 35 minutes explaining the problem, then measuring the radio outputs and testing to see that the Arduino can read them accurately. Because the radio has a very large range of operation, [Todd] will need to add external component to facilitate this. That extra circuit design will be the topic of the next project segment.

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7400 Frequency Counter

November 6, 2012 by 12 Comments

This frequency counter is [Miguel Pedroso’s] entry in the 7400 Logic contest. After looking at the design we think this is a perfect project for those who have not worked with logic ICs before. The concept is simple and [Miguel] does a great job of explaining his implementation.

At its heart the device simply counts the oscillations of an input signal for one second, then latches the total to the 7-segment displays before zeroing the counter block and starting over. Six 4029 decade counters give the device a range of 1MHz. A set of 4511 BCD to 7-segment decoders translate the count to the display. A 4521 frequency divider chip uses an on-board 4.194304 MHz crystal oscillator to time both the display latching and the counter clearing. [Miguel] mentions that tuning the load capacitors is a bit tricky. Since breadboards have their own capacitance issues it may be necessary to change the load capacitor values when moved to protoboard or the crystal won’t start oscillating. You can see those caps are not the same value, but the tests in the video after the break show that this is pretty much spot-on.

If you’d rather give this a try in HDL here’s an FPGA-based frequency counter from which you can draw some inspiration.

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Building A 100 MHz Frequency Counter

November 2, 2012 by 5 Comments

The great thing about building with gates is the crazy speeds you can achieve by using hardware directly (as opposed to working with simple microcontrollers). This 100 MHz frequency counter is a great example. [Michael] just finished building it using a Papilio board.

Of course we’re not talking about discreet chips here. The Papilio is an FPGA development board which means he is building with hardware gates, but that is still done by writing code. Above, the rig is measuring a 25 MHz being generated by a second FPGA board. Using the Papilio’s on board 32 MHz clock the device is capable of counting a frequency up to 100 MHz. You can see it measuring a 96.875  MHz signal in the video after the break. One interesting thing about that clip is that near the end he touches the crystal’s case with his finger and the Hertz really jump for a moment.

If the 8-digit display looks familiar that’s because [Michael] recently published a library to use it with an FPGA.

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Adding USB Connectivity To Old Benchtop Tools

July 25, 2011 by 7 Comments

frequency_counter_hacked_for_usb_connectivity

[Scott] was recently given a frequency counter, and once he brought it home, he started contemplating how he could possibly make it better. While the counter worked well as-is, he wanted to find a way to record data readings over a reasonably long period of time. He figured that interfacing it with his computer would be the best way to do this, but he had to find a way to connect the devices first.

He started poking around inside the frequency counter and stumbled upon a possible data source when taking a closer look at the display board. He found that he could read the frequency data as it was being written to the display, and send that data to his computer. He used an ATMega48 to intercept the data and code from the V-USB project to bit-bang the data to his PC over USB.

Now, anything he sees on the frequency counter can be easily collected and graphed on his computer with little fuss.

Stick around to see a quick video demonstration of his hack in action.

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Precision Frequency Measurement Library For 8-bit Microcontrollers

June 3, 2011 by 7 Comments

[Paul] has been working on porting over Arduino libraries for use with the Teensy microcontroller platform. This tends to be pretty simple since they both use the same Atmel chip architecture. But once in a while he finds the Arduino libraries are not what they’re cracked up to be. When looking to port over a frequency measurement library he ended up writing his own that works better and is much more portable.

He had two big beefs with the Arduino Frequency Counter Library. The first is that it required the compensation factor the be calibrated using an accurate frequency counter. That’s a chick-and-egg problem since many people who build a frequency counter with an Arduino are doing so because they don’t already have a standalone tool. The second problem is that the Arduino library was hardcoded for ATmega168 or ATmega328 chips.

This new library fixes both issues with just one trade-off. Your hardware setup must be using a crystal oscillator. You can see above in the image above that the frequency measurement is quite accurate with this method. The package also uses a thin abstraction layer which will make it easy to port to any 8-bit microcontroller which is programmed in C.

PIC Based Frequency Counter

March 15, 2011 by 6 Comments

Here’s a PIC based frequency counter that outputs the count via an RS232 serial connection. [Oakkar7] tipped us off about it after seeing the AVR based counter we featured yesterday. This project is a bit older and a bit dirtier.

Inside the metal DB9 housing you’ll find just seven parts. The most important is a PIC 16F628 which handles both the counting and the serial communications. We’re not quite sure how it’s managing to talk to that USB-to-Serial converter without some type of level conversion. Since this microcontroller is not a dedicated counter chip a little bit of trimming must be done to bring the accuracy into spec. There’s also some physical trimming involved. In order to get everything to fit into the small enclosure the circuit was free-formed without a PCB or protoboard and the case of the DIP chip had to be ground down just a bit. As for the readout, a simple script can grab the data and display it in a terminal.

[via Piclist]