Complete SMD HCMOS Frequency Meter

At this address I have published the project of a frequency meter made with HCMOS integrated circuits in the SMD technique.

Starting from these, I continue to show a construction (in 2 versions) of a complete frequency meter that can receive a low-level input signal and a shape different from the rectangular one (usually sinusoidal signals are measured).

The first version, hereinafter referred to as ACVer, is physically realized on 2 PCBs arranged perpendicularly and is made with LEDdisplays, Common Anode variant. This version lends itself well to panel mounting of devices.

The second version, hereinafter called CCVer, is made with LEDdisplais in the Common Cathode version and is made on a single PCB.

Both variants have two separate and switchable inputs to which low-level sine signals can be applied and which provide HCMOS-level square-wave signals at the outputs.We will call them "signal shapers".

Today, these frequency meters are considered obsolete, having been overtaken by those with microcontrollers.

However, the low cost price and especially the high reliability and easier troubleshooting possibilities of the device described here should be considered. These qualities recommend him.

All electronic components are in current production and can be purchased from here.

PCBs can be ordered from here.

Electronic components and PCBs can be purchased from other places, there are many sites specialized in this.

For those who have the technical possibilities to make PCBs, they can be made on their own, according to Step3 instructions.

The article I referred to in the "Introduction" describes in detail the operation of the wiring diagram on the digital section. So we won't repeat it here, just describing the signal shapers part and powering the device.

ACVer (see Photo with title P2)

Signal shaper A- it is made with Q10, Q12 and is a broadband amplifier with very high amplification.The signal from jack J2 is applied to the first grid in Q10 which has the role of a buffer and an amplification of approx. 3 .The signal thus obtained is applied to the base of Q12, which is a broadband amplifier and amplifies by hundreds. In the collector of this transistor we will find a limited signal higher than the value of the supply voltage (+5V) and down to 0V, which is exactly what is needed.The output pulses have the same frequency as the input signal.

Signal shaper B- Is made with U13, Q11. It is followed by two frequency dividers made with U15, U21.The input signal from jack J3 is applied to input U13 (U664B), which is a specialized ECL circuit that takes this signal and divides its frequency by 64.The signal from the output U13 has ECL level. Therefore, Q11 is necessary, which brings the ECL level to HCMOS, necessary for the operation of U15.The signal from the Q11 collector is successively divided in frequency 3 times. Twice with the two U15-dividers and once with a U21-divider (the second one is unused). Each time, a so-called division by 2.5 is made, in the sense that for 5 input pulses, two are obtained at the output. Thus the global division factor is 64X2.5X2.5X2.5=1000.So the signal from J3 is amplified and divided in frequency by 1000.This signal is obtained at pin11 U21.

U22 switches at your choice (via Sw1 on P1) the signal from the output of one of the formers to the main counting gate.

CCVer: see Photo with title "6 digit SMD frequency meter"

Signal shaper A- it is made with Q7, Q8 and is identical to Signal shaper A from ACVer.

Signal shaper B- Is made with U23 (U24), Q9. It is followed by two frequency dividers made with U29, U30.The input signal from jack J4 is applied to input U23(24) (type MB506), which is a specialized ECL circuit that takes this signal and divides its frequency by 64. MB506 is produced in the THT or SMD version. The PCB is designed to use either variant. For PCB design reasons, 2 ICs, U23 and U24, are shown on the basic electrical diagram. Obviously, the available version will be used.The signal from the output U23(24) has ECL level. Therefore, Q11 is necessary, which brings the ECL level to HCMOS, necessary for the operation of U29. As in the case of ACVer, the total division factor is 1000.

Sw1 switches at your choice the signal from the output of one of the formers to the main counting gate.

Because datasheets for MB506 and U664B are harder to find, I give them below.

A particularity of these schemes that contain signal shapers, is that the supply voltage (+5V) must not contain ripple, otherwise the formers present a phenomenon of self-oscillation even without an input signal. This requires the supply with +5V from a linear stabilizer type LM7805 as in Photo1.1.At the input, the 7805 can be powered with a +9V switching power supply.

I personally used a 9V/1A switching power supply, like the one in Photo1.2.

In its case, I inserted the LM7805 (on a small radiator) and C=10uF/16V. There is space inside. I connected them as in the diagram in Photo1.2 and gave the voltage of +5V on the output cable of the power supply.

The ACVar project can be found at:

https://oshwlab.com/TedyS/6-digit-digital-frequency-meter for P1 and:

https://oshwlab.com/TedyS/6-digit-digital-frequency-meter-p2 for P2

The CCVar project can be found at:

https://oshwlab.com/TedyS/frecv-1-placa-var-2

From here we can obtain the BOM (bill of materials), very useful in the supply of components.

Photo 2.1 shows the small assembly bench I used and some CCVar frequency counters at various stages of assembly.

Photo 2.2 shows other necessary tools.

In addition to these, the following are necessary:

-10MHz oscilloscope and attached probe.

-Pulse generator and attached cable.

-Sinusoidal signal generator with calibrated output attenuator, from 100KHz to minimum 1GHz or even more.

-Digital multimeter.

Information regarding the execution of PCBs can be found in the links given in the previous step. They can be ordered directly from here, or using the Gerber files, they can be ordered from another manufacturer or made on their own.

I ordered the PCBs and they look like in Photo 3.1 when they arrived.

Photo 3.2 shows the PCBs (P1 and P2) for ACVar. Photo 3.3 and 3.4 are 2D images for the same PCBs.

Photo 3.5 shows the PCB for the CCVar, and Photo 3.6 is a 2D image for it.

Assembling the PCBs can be done using the data from the links from Step2 or the 2D images from Step3.

A good tutorial for soldering SMD components is given here. I personally used the soldering method with a soldering station using the tools shown in Step2.

The SMD components will all be mounted at the beginning, following the THT ones.

For ACVar, P1 will be solder perpendicular to P2 after make to work the 2 plates. The two J1 couplers on P1 and P2 will be soldered pin to pin with tin.

Photo 4.4 and 4.5 show P1 and P2 assembled with components, front and back.

Photos4.6, 4.7, 4.8 show ACVar with P1 and P2 mounted, from various angles.

Photos 4.9, 4.10 show the assembled CCVar, front and back. In the last photo you can see some corrections (PCB restorations, marked in red) due to small errors in the PCB design. These errors have been corrected in the PCB project that can be downloaded from here (Step2).

Making the digital part to work and calibrating it is done in both versions as with the devices in the link from the Introduction, so we will not repeat it here.

After this is done, we will make the signal shapers work.

ACVar InputA : A signal of approx. 30mVef/1MHz is applied to the J2 plug from the sinusoidal signal generator.This signal will be amplified 3...4 times in the drain of Q10. At the collector of Q12 there will be a HCMOS level signal (5V amplitude) of the same frequency as the input. This is a fair level for the main gate attack.

InputB : A signal of approx. 30mVef/50MHz is applied to the J3 plug from the sinusoidal signal generator. At the output of U13 (pin6) there will be an ECL level signal with a frequency 64 times lower than that of the input signal, approx. 781KHz. Q11 will amplify this signal to a HCMOS level, which we will find in its collector. Next, this signal is divided 3 times by U15, U21. At its output (pin10 to U21) we will have a total frequency division of the input signal of 1000, so a 50 KHz signal.

CCVar InputA : Identical to the previous version.

InputB : A signal of approx. 30mVef/50MHz is applied to the J4 plug from the sinusoidal signal generator. At the output of U23(24) (pin4) there will be an ECL level signal with a frequency 64 times lower than that of the input signal,approx. 781KHz. Q9 will amplify this signal to a HCMOS level, which we will find in its collector. Next, this signal is divided 3 times by U29, U30. At its output (pin10 to U30) we will have a total frequency division of the input signal of 1000, so a 50 KHz signal.

Electrical performance:

ACVar : InputA: - Sensitivity: 30mVef

- Frequency range: 100KHz....65MHz

InputB: - Sensitivity: 30mVef

- Frequency range: 30MHz....1,05 GHz

CCVar : InputA: -identical to InputA from ACVer

InputB: -Sensitivity: 30mVef

-Frequency range: 30MHz....2,4 GHz GHz (tested up to 1.5GHz). Although in the datasheet the minimum working frequency is given as the value of 100MHZ, all the samples of MB506 tested by me dropped below 30MHZ with an input sensitivity of 30 mVef.Due to the very high amplification and high sensitivity, in the absence of the input signal MB506 will self-oscillate on a frequency of 10...20MHz, even with a short circuit at the input.

For both variants:

-display on 6 red digits

-the value is displayed in KHz for InputA and MHz for InputB, signaled by LEDs.

-they can connect to the 2 different signal inputs, which will be displayed at your choice

-supply voltage: +5V with small ripple, linear stabilizer

-consumption from the +5V source: approx. 400mA. most of the consumption being given by the LEDdisplay

The gauge dimensions are:

90X45X50 mm for ACVer and

95X95 mm for CCver

Being very precise, the device finds its usefulness in the field of electrical measurements,ham radio, and others.

And that's it!