using twelve light emitting diodes. The prototype has a CD4040 as counter and a CD4060 as the timebase generator. Gating the signal is by a resistor - diode gate. CMOS ics used here allow the instrument to be powered by any voltage in the range of 5 to 15 volts, but the maximum frequency is limited to about 4 MHz.

The 4040 is a twelve stage binary counter in a 16 pin package. The 4060 is a fourteen stage binary counter and oscillator, in the same 16 pin package.

The 74HC or 74HCT versions of these chips may be used for a higher frequency range, but the supply voltage range is then limited to a maximum of 5.5 volts or so.

In order to use this in order to display the frequency of a typical HAM transmitter, some sort of a prescaler and a preamplifier will be needed. Hopefully these shall be the subject of a subsequent instructable.

Step 1: Twelve LED Array

I started on this project in order to have a simple frequency counter which would work with the minimum of hassle, using the fewest number of components and NO programming. I settled on this "two chip frequency counter" design because its simplicity was appealing.

The first step was to wire the counter and make it work. I rounded up a number of red 3mm leds from my junk box and various boards and soldered them up in line on a sliver of circuit board - the result is shown here next to the counter chip. This particular ic was extracted from another half-finished project, with the fervent hope that at least this one will end up finished.

The 74HC4040 will be a better choice if you are planning on building this. It can count to a higher frequency.
Hello, <br>This is a great circuit thank you for posting it. <br>could you tell me if i can drop the frequency from the Mhz range to khz range, <br>i need to get a rough measurement from 20k to about 100 or maybe 150khz <br>Thank you and thanks again for this post.
has anyone got a schematic for a LED meter that only uses a diode, capacitor, resistors and LED's? no chips or transistors just the listed components :) I have seen it as a kit in plenty of places but no schematic :(
this is a dutch site but the scetmatic is readable i think<br/><a rel="nofollow" href="http://www.circuitsonline.net/circuits/view/59">http://www.circuitsonline.net/circuits/view/59</a><br/>the text says that pin 9 and pin 3 have to be connected to get bar mode<br/>
thnx ;) but i did say "no" chips or transistors :) just resistors and diodes..
oh did not read it right:P:+ sorry:P
no probs ;)
bong your best bet for construction is a diode latter, remember each diode drops the voltage by a fixed amount, and different diodes have different drops. They also have a triggering voltage dependent on the type, meaning a minimal voltage to pass through. so know u have the equivalent for a Voltage based bandpass. I guess a voltage pass filter?. you can use the same concept using band pass filters, or high pass and low pass. but you might have to derectify for each step in precision. Im not not an ee so i cant really give you exact parts or anything. but hopefully can guide u in the right direction.
thnx i'll look into it ;)
Wow. If I had ever fooled myself into thinking I had any prayer of learning anything about electronics, I now know better. I can appreciate the time and effort this took, and I can also appreciate the thoroughness of it. That's where it's usefulness stops for me. I don't even know what it is, or what it does. I hope this helps some of you guys out there! Nicely done. ;-)
yes it was very helpful, i just build one, works well

About This Instructable




Bio: Hi. I'm Chandra Sekhar, and I live at the southern tip of the Indian subcontinent. I'm interested in building small one-off circuits around ... More »
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