16Mhz Crystal Oscillator Actually at 16Mhz!

Again, due to the breadboard affects on crystals, my  circuit was slightly different than Alan’s by the lucky trial and error of my incorrect cap value components removal – including a floating caramic cap at the base of TR1 – at full PSU 30V before this thing kick started at a stable 15.9982MHz.

I removed the top 10nF cap and one 470pF (mine was a different value anyway) from ground., leaving one floating…(aerial!?). So touchy! Just connecting the probe ground can stop it..

17V gives a 1Vpp sine wave – if you don’t move anything!:

3 Transistor Sawtooth Generator / Oscillator

yeah…a really shitty circuit, took fkin ages!! I had to run at 29V and kick start it by pulling and reconnecting a jumper to the emitter of the 2nd pnp tranny. If I dropped voltage below 24V it would stop again…2nd probe would also cut it off on contact. Total pain and batshit noisy. The resistor values aren’t close enough to my transistor 0.7V turn on – got mostly 0.56V at the bases, hence higher voltage req.

LM358 VCO Circuit

This isn’t clear for beginners, but V/2 at pin 5 non-inverting input of amp 2 means you have to add another 2 x say, 10k resistors as a voltage divider to supply the correct voltage at pin 5 – NOT the full PSU voltage (5V) as I did at first – else it won’t work.

The pin 5 100k/51k resistors are the feedback, not the voltage dividers..duh!

With a 47uF cap at pins 1-2 I get the correct outputs:

Kentiger HY-502S Amp

These are good amps for the size, function and cost – if you have a 3-5A, 12V PSU already?!

They can be improved by modding according to:


..agreed, those LEDs are annoying, better if they had been volume levels, not a disco..

Ok, you can buy a classic 90s used amp on Ebay for that £30+ total of PSU also, but if you want small, light (and free electric shocks!), but still good sound, this is worth it for the functions – USB and SD card for MP3; radio, remote control and about a 10W RMS output. Loud enough for most rooms.

I’ll do some tests…

Two Transistor Schmitt Trigger; Converts Analogue Signal to Digital Output

This essential circuit converts an analogue signal to a digital output and also creates fast rise and fall time square waves:

Transistor Schmitt Trigger

This circuit gives a max output of 3.8V digital from a 3.8V sine input;

The Vcc can be no more than 5V else the top threshold of this circuit design is crossed and the output goes to 0V; the input must be no less than 3.7 Vpp AC else the lower threshold won’t be crossed and trigger a change, due to the concept of a Schmitt Trigger:


“It is an active circuit which converts an analogue input signal to a digital output signal. The circuit is named a “trigger” because the output retains its value until the input changes sufficiently to trigger a change. In the non-inverting configuration, when the input is higher than a chosen threshold, the output is high. When the input is below a different (lower) chosen threshold the output is low, and when the input is between the two levels the output retains its value. This dual threshold action is called hysteresis and implies that the Schmitt trigger possesses memory and can act as a bistable multivibrator (latch or flip-flop). There is a close relation between the two kinds of circuits: a Schmitt trigger can be converted into a latch and a latch can be converted into a Schmitt trigger.

Schmitt trigger devices are typically used in signal conditioning applications to remove noise from signals used in digital circuits, particularly mechanical contact bounce in switches.”

I found changing R2 to 30k and increasing Vcc to 5.4V I got a 5V logic level for a 3.6Vpp input:

The closest I got to a 5V, 50% duty cycle square wave was a 3:2 rectangle by changing R1 to 10k and Vcc at 6.8V – an insight to circuit design and limitations like power feed, component stress and stability etc.

LM358N/TL082/741 Op Amps 5 Gain Circuits and 741 Op Amp Tester Circuit


lm358n 5 gain cct: 30V DC (max V = < 33V!), gain of 5 circuit Rf = 100k (pins 2 to 1); Rin (pin2),2Vpp sine input , inverting)= 20k; voltage divider 2 x 10k for 15V at pin3 (non inverting); clipping starts at 27.5Vpp for a 5.4Vpp input. This circuit swings quite close to within 2.5Vpp to rail voltage of 30V. Gain = 27.4÷5.36 = 5.11

Use the same cct as the dual amp lm358 for the dual tl082 as pinouts are same, so exact same gain results as lm358:

The 5 gain circuit only needs minor changes but at only 20V max PSU , not 30V!! (pins 8-7; 1-6) to use the 741 single amp package for same results for gain, as you would expect. The real FR of op amps is into the 100kHz ranges, not my 17kHZ phone out limits:

Note diagram pin 7 error of 30V – should be 20V:

With the addition of the 0.01uF feedback cap from w2aew’s circuit:

from output pin 6 to inverting input 2 of the 5 gain circuit you can see the same linear dis/charging of the cap if a square wave is input. Note how it bypasses the 5 gain 100k back to unity gain :

Op Amp tester circuit:

“We just need to place the op-amp LM741 on right place and if the Op-amp is in good condition then LED will flash or Blinks, and if Op-amp is faulty then either LED will remain ON or OFF continuously.

Working of the circuit is simple, basically this circuit generates a Square wave at the output if op-amp is in working condition, resulting a Blinking LED. When we ON the circuit with op-amp is in place, initially voltage at non-inverting input (+) is higher than the voltage at inverting input (-) and output of op-amp LM741 (PIN 6) is High. So capacitor C1 starts charging through the resistor R6, when C1 charging exceeds the voltage at inverting terminal (PIN 2), then output becomes low. And when the output goes Low, capacitor C1 starts discharging and again voltage at inverting terminal of comparator becomes lower than non-inverting terminal and output goes High. This process repeats continuously and produces Square Wave at the output, which causes LED to Blink.

So if the Op-amp is in working condition, then LED will blink continuously at regular interval and if op-amp is faulty then LED will either stays ON or OFF.

This process of charging and discharging of capacitor is much similar to 555 timer IC in Astable mode, which also produces square wave at the output.”

It’s useful so I built it on perf board:


Reading Remote Control Codes With Arduino

Old remotes can be re-purposed:

Following this Post using the IR sensor connections – forget the LEDs just for reading codes:


an old Philips TV remote showed codes for buttons 1-0 and Off – note contact bounce repeats;

01:20:47.878 -> 9985
01:20:48.010 -> 9985
01:20:50.492 -> 9986
01:20:54.363 -> 9987
01:20:54.462 -> 9987
01:20:56.845 -> 9988
01:20:56.944 -> 9988
01:20:58.201 -> 9989
01:20:58.301 -> 9989
01:21:00.121 -> 9990
01:21:00.220 -> 9990
01:21:01.610 -> 9991
01:21:01.709 -> 9991
01:21:02.999 -> 9992
01:21:03.099 -> 9992
01:21:05.084 -> 9993
01:21:05.183 -> 9993
01:21:06.507 -> 9984
01:21:06.639 -> 9984
01:21:14.778 -> 9996
01:21:17.624 -> 9996
01:21:19.510 -> 9996

Simplest Transistor Oscillator and Breadboard Crystal Oscillator Actually Working!

To have a more complete understanding of today’s networked tech world, you have to link some key electronic fundamentals to the OSI layer 1 area of IT networking that deals with the actual voltages that generate binary values 1 and 0 that have to be regulated/counted with reference to time of an accurate reference clock of some sort e.g. an oscillator circuit, to then be counted, grouped then streamed or stored in various ways according to some set rules or protocols like I2C, ADSL, Ethernet etc. See my Post on encapsulation for more info:


These clocks can come in many forms from different natural or man made sources – pendulum, tuning fork, atomic decay, light wave frequency, piezo crystals or other electronic components that oscillate periodically, and hopefully consistently over “time” itself!

The more consistent, the more accurate and useful they are – see the history of the Longtitude Clock prize for navigation for perspective!:


The simplest powered oscillator circuit I’ve found is below:

A “reversed” NPN transistor (I used a 2n2222) with floating base and reversed voltages breaks down at about 12V or more, causing oscillation. Try different V, R and C values to alter the Time Constant, T=RC. Be mindful of minimum resistor values to not fry the tranny or LED (<20mA)

For accurate electronic time for very cheap, the Quartz Crystal oscillator is used in almost every circuit on most devices – ever!

They can be really difficult to get going on a breadboard due to high frequency noise and bad connections causing capacitance issues – and they won’t necessarily run at their stated frequency, but at a harmonic vibration above their fundamental tone. It took 5 different attempts over 3 days with different circuits to get this 16 MHz crystal stable and working – but at 23.3xxx MHz not 16!

The next step would be to feed this into circuitry that would generate, say 5V logic square waves instead of the sine wave then divide the rate down to suit your desired bus speed…get the general idea?