Frequency is very important parameter of any signal. No matter if you are generating or synthesizing signals, you most likely need to measure its frequency. When signal frequency is bellow 40kHz and amplitude is near 5V then you can build frequency counter on Arduino with standard LCD screen. If measure signal is 5V (or 3.3V) level then you can feed it directly in to Arduino input. In other cases you need to use limiting circuit like amplifier or voltage divider. But this small project assumes that voltage is fed directly to microcontroller input.
In this example signal comes to digital pin 12 where function pulseIn() counts number of pulses during specified time. Program itself is only few lines of code, and hardware is straight forward so putting it to work condition is only a matter of minutes.
This frequency counter is practically classic example of MCU based device. It captures frequency pulses directly to MCY pin without any special prescalling circuitry or even protection. So it is capable to accept 3.3V CMOS level signals. But it is designed as module which can be integrated in to end device if needed. The counting workload is done by MSP430G2202 microcontroller which is capable to count up to 10MHz signals.
The display is connected to microcontroller using transistor based column selector decoded by 74HC238 and rows driven by MCU pins. One interesting feature included in this project is that counter can be calibrated to achieve +-10Hz error at 10MHz.
What does it take to measure frequency up to 100MHz. The answer is FPGA. Mike wanted to make pretty accurate frequency counter so grabbed Papilio FPGA board, attached TM1638 display board from DE and referenced frequency with GPS module. It works without GPS module but looses accuracy since these modules may give 1PPS with accuracy down to 20ns.
Well, some of you here might have built a few PIC frequency counter before, and fully understand about its usability in the electronic field. However, for those who never get in touch with PIC frequency counter, it’s an electronic instrument that being used for measuring frequency.
Technically, frequency is defined as the number of events of a particular sort occurring in a set period of time. In order to measure the frequency, you have to use a counter to accumulate the number of events occurring within a specific time. Let’s say, after a preset period (1 minute, for example), the value in the counter is to be reset to zero automatically!
By the way, we’re going to build an IK3OIL 16F84 PIC Frequency Counter. Most people are worry, as they might need to waste a lot of money buying the electronic components. Well, you know what? This IK3OIL 16F84 PIC Frequency Counter is very cheap, as the cost of the counter is cost you about US$2, while the display is only less than US$5!
Frankly, this IK3OIL 16F84 PIC Frequency Counter is a marvelous frequency counter, as it not only cheap, but can perform a better result than other frequency counter did!