Scullcom Hobby Electronics #41 - Design & Build a Stair-Step Generator

[@harveyellis6758]

Another very nice project from one of the best instructional sources for electronics on KZbin. I'm very happy to see you back online again.

[@scullcomhobbyelectronics1702]

Thanks Harvey.

[@berniken6511]

Excellent project Louis as usual, good to see you back...........................Berni

[@scullcomhobbyelectronics1702]

Thanks Berni.

[@IlhanNegis]

Is it just me? This is as soothing as Michael Caine explaining an oscillator circuit.

[@scullcomhobbyelectronics1702]

Interesting, I had to smile at your comment !!!

[@KarlA-vk4kn]

Great project. Like the options to give you stepped ramp waveforms also 👍👏👏

[@NearFarMedia]

Great project and explanation as always. First time I've heard of a Johnson counter. Thanks!

[@scullcomhobbyelectronics1702]

Thank you.

[@outofround]

Love those Johnson counters!

[@jct4647]

Excellent design & build tutorial, thanks.

[@scullcomhobbyelectronics1702]

Thanks.

[@cccyberfamilydk]

Nice Video. (again) :) Good to see you back.

[@scullcomhobbyelectronics1702]

Thanks again. Just lately I have been busy with other commitments. Hope to upload a new project in the next few days.

[@qamarkilani551]

Another Great Video ... Many Thanks for your amazing projects

[@scullcomhobbyelectronics1702]

Thanks.

[@andrewferg8737]

Great video.Thanks for sharing! I built it and it works, however after further research I decided to use an R2R resistor ladder instead of your binary ladder. The R2R was more stable and simpler to implement.

[@andrewferg8737]

Great video! Very clear presentation.

[@Roy_Tellason]

I've seen the comments about you grounding the Q9 output, which I will also say that you should never ever do. In addition, you appear to routinely allow violation of the rule that says that ALL CMOS inputs have to go somewhere. In this unit, the clock input to the 4017 should have a 100K resistor to ground so that it's not floating when the switch is moved, or when links are not in place, even if that's during a transition in your setup. I also notice that the alternate waveforms step on the way up but not on the way down like the primary waveform does. I don't see a need for that "rail spliiter" chip when you can accomplish the same thing with a couple of resistors, maybe also a couple of capacitors across them. Finally, your staircase output has one ground reference and your sync output has a different one. This could come back and bite you in the ass at some point...

[@zx8401ztv]

Smashing project :-D And for more steps you can add another 4017 :-D Ahh the johnson counter, a very handy i.c :-D, i last used one to select the supply voltage to an eprom/flash programmer. The Q outputs drove transistors that connected to a selection of resistors connected to a lm317 adjustable regulator. The clock input was a push button and passive parts so i could press the button and the johnson would step, simple and crude but it worked a treat :-D.

[@scullcomhobbyelectronics1702]

Thanks. As you say using the Johnson Counter to control switching is a nice option. Like you I used it many years ago to act as a selector switch with a push button stepping the clock input at each press, giving 10 switch positions with one button. You do not see this IC used very much these days but it is still a very useful IC.

[@zx8401ztv]

When i used to repair c.b radios i was often asked to fit a "K" tone or 5 tone roger bleep, they used the old 4017 too, a couple of 40xx chips for oscilators and control, Plus r/c and diodes on the output of the 4017 lol, they worked very well :-D Im a bit old fashoned, i like the 7400 and 4000 series logic better than any other method :-)

[@scullcomhobbyelectronics1702]

c. b. radios that takes me back. Not used much these days. I still have a couple of Binatone c.b. radios under the workbench in a box! I use to play around with surplus Second World War transceivers such as the 38 Set and the 19 set. Long time ago now !!!

[@zx8401ztv]

The popular binatone 5 star was a good cb radio, silver fasia, the pcb was a cybernet ptbm134, same as quite a lot of the popular radios around in the mid 80's. Uniden radios like the uniace 100/200 or realistic trc2001 and similar were another choice. . Cb radios is where i learnt synthesisers/rx i.f stages and tx mixers/power stages. Other parts were often discrete transistor circuits or an op amp for the tx audio and a power amp chip for the receive and sometimes tx audio. I repaired a lot of the uk radios for truck drivers for years, some so called cb repairers left radios in a mess, they also came here to be corrected. c.b lead me on to repearing multiband/multimode cb radios and repairing some ham radios. C.b was a good way to learn radio/antenna/swr :-D

[@fieldsofomagh]

Like the scope display to illustrate the theory.

[@scullcomhobbyelectronics1702]

Thanks.

[@pirateman1966]

At 5:15, you connect the OUTPUT Q9 to ground? say goodbye to that pin if it's TTL! You need a 10k+ resistor to ground, if you are worried about noise immunity. Unused outputs are left floating, while unused inputs, are grounded or pulled up to +Vcc. Is that not the common practice now a days? I'm not sure what this circuit is used for? I can generate 1024 step wave forms with an $2 Arduino clone + an op amp if I need to generate audio wave forms of any shape. No?

[@GADELHAS82]

Great as always! You could also use the voltage divider formula, to find out the resistors values! Thanks

[@scullcomhobbyelectronics1702]

Thanks. Yes you could use the voltage divider formula.

[@magdalenajirova5745]

I like the thorough way you explain your circuits. Are you a teacher of some sort?

[@scullcomhobbyelectronics1702]

Thanks for your comment. Many years ago in the 1970's I did teach electronics for about 7 years but then move in to management. You can check out my personal profile on my website if you are interested from the link below: www.scullcom.uk/about/

[@Gooberslot]

Why did you remove the 0.1% resistor because it looks like at 31:00 that you have them installed but later on when you're testing the board they're gone?

[@scullcomhobbyelectronics1702]

Well spotted. In my early testing I used some different value resistor (higher values) and at that time I used 0.1% tolerance and that is what you see in the video. As the video was getting to long I cut out some of the video footage in the final version. In the final version I used the resistor values I indicate in the video which I found to be the best choice. Initially I changed them to standard value 1% resistors of 7.5K, 3.3K, 1.8K, 1K and 560ohm and it did work very well as you see in the video so I decided to show that. In my final version I did replace them with 0.1% tolerance but did not film that, these gave a similar result but the accuracy of the steps were improved. I have shown the 0.1% resistors in the parts list with RS Components Ltd stock codes.

[@MsFireboy2]

Question would this circuit be useful in a curve tracer application? Thoughts readers?

[@Niftypsycho]

The diodes on the outputs are to protect them from one another when they drive the same resistor right?

[@scullcomhobbyelectronics1702]

Thanks. Correct.

[@alien8r33d]

Am I missing something here, unused OUTPUT Q9 tied to GND???

[@hlavaatch]

That is of course wrong. You ground unused INPUTS.

[@scullcomhobbyelectronics1702]

Thanks for your comment. SeanBZA also brought up this point which I have replied to below. Q9 can be left disconnected or alternatively you could ground it with a 10K resistor.

[@rndqrp1256]

Is it interresting to add some voltage reference in your circuit ? And adding some pf cap for filtering your step's signal ? Why not using a DAC to generate your stairstep-ramp which could control your VCO too through a PLL. 74HC161, 74HC160, 74HC4046. Is this more accurate than digital ramp use in a DVM ?

[@scullcomhobbyelectronics1702]

Hi, thanks for your comment. There are many options in producing a stair-step generator. In my project I wanted to demonstrate the use of a Johnson Counter. If you wish you could use a DAC other counter IC's as you suggest. You could even do it with a micro chip. There are lots of options. My project is just my take on one example. I would imagine a digital stair-step ramp used in some types of DVM's would be more accurate as it makes its voltage measurements by comparing the input voltage to an internally generated stair-step ramp voltage which is set/calibrated during manufacture. Regards, Louis

[@rndqrp1256]

Hi, Thank's for your quick answer and Thank's 4 your video's Renaud Last question: What about making a frequency ramp or "stairstep" may be around 10Mhz from let's say from 9.5 to 10.5 Meg -10dbm step from -80dbm to -30dbm with why not a si5351.. ;-)

[@calabrese1531]

One of the hardest tasks of measuring passive components is the measurement of inductors. I googled some projects of diy LC meters but I couldn't find any project as satisfactory as of simplicity, accuracy and with no micro controller though. I found out, whatsoever, that it might be possible to design such meter with a tank circuit, a 555 oscillator and an LM331 frequency to voltage converter IC. What do you think, is it possible to design and build a simple yet accurate LC meter with those components? I think it can be an interesting project.

[@scullcomhobbyelectronics1702]

Thanks for your comments. Many years ago I made a capacitor meter using a NE555 timer IC which worked very well. So yes it is possible to build an LC meter using a 555 timer.

[@calabrese1531]

Thank you very much for your videos, they are very well explained and appreciated by hobbyists. Sadly you don't have a video about designing and building an LC meter with a 555 IC. I think a lot of people would find it very interesting and useful. I know there are many cheap already made solutions in ebay but the idea is to learn and the joy of designing one for yourself, but some of us lack of the ability and knowledge that you have. Maybe one of these days you can make a video about it.

[@SureshKumar-nk2ok]

thank you very much sir for valuable guide .

[@scullcomhobbyelectronics1702]

You are most welcome.

[@SeanBZA]

Grounding Q9 will not make the chip happy, though at 5V a CD4017 will survive, but the 74HC4017 will be running the output into a short, which causes a very large current pulse in the chip, which is not good. Just leave it open instead, which will do nothing. This output will have a temperature sensitivity, which can be compensated for somewhat ( will not track perfectly but better in most cases) by using another 1N4148 in the ground lead of the 7805 so the supply is 0.6V higher, which will also track temperature wise with the other diodes somewhat. Better would be some low leakage Shottky diodes in place of the 1N4148 diodes, so the drop is lower. Increasing supply by 0.6V will not worry most of the TTL at all, most is very happy with 4.5 to 5.6V in most cases.

[@Alo762]

And he says that connecting it to the ground reduces noise. Actually, it adds noise, namely 10kHz signal with odd harmonics. I would like to see the current consumption in one channel of the oscilloscope!

[@scullcomhobbyelectronics1702]

Thanks for your comments/suggestions. In practice I have found that there is virtually no difference in current. With Q9 left disconnected the total current consumption of this project is 19.13mA and with Q9 grounded it is 19.56mA. I do however agree with your suggestion to simply leave Q9 output disconnected. Alternatively you could ground it with a 10K resistor in which case the total current would remain at 19.13mA. Your suggestion of replacing the 1N4148 diodes with Schottky diodes is a nice option as a Schottky diode have a lower forward voltage drop, about half that of a silicon diode. This allows for faster switching speeds so would result in a cleaner stair-step at higher frequencies. However, my understanding of Schottky diodes is that they are extremely sensitive to temperature because of there high leakage characteristics so if temperature is an issue then they could cause problems. But with regards this project I do not feel that temperature is an issue anyway.

[@Alo762]

Would be interesting to see Q9 connected to ground thorugh eg. 5 ohm resistor and the seeing the voltage of that pin in oscilloscope. Per TI datasheets, HC logic output can give up to 70mA of current but based on your finding on the average current consumption difference, I would expect to see about 4mA current pulses which, over 5 ohm resistor would mean about 20mV pulses over the resistor. In any case, you should NEVER connect logic outputs to rigid ground or supply. NEVER. It is just plain wrong. In the worst case, the resulting current may destroy the chip.

[@scullcomhobbyelectronics1702]

Thanks for your input which is welcome.

[@andrewferg8737]

True gold! Was bingeing on your home page playlist just now. Glad I found it! Curious why there are five outputs... Will it work with four? I'd like to have a go at using this with a discrete step motor driver I've built.

[@PelDaddy]

Nice to see you back online. Was beginning to get worried. I keep thinking of Devo when I see the output of of this thing! Why buffer before the amplifier, rather than after? Curious which is preferred and why? Thanks for all the great videos!

[@scullcomhobbyelectronics1702]

Thanks. You can buffer before or after the amplifier as it should make very little difference in this case.

[@SureshKumar-nk2ok]

thank you very much sir

[@scullcomhobbyelectronics1702]

You are welcome.

[@paulfletcher848]

Shouldn't Q9 be fed back to RESET to limit the sequence to 9 steps? That how I always used the 4017 on light sequencers back in the 80's

[@scullcomhobbyelectronics1702]

Thanks Paul for your comment, good question. If you connect Q9 to the reset you would loose the bottom step of the waveform. This would then result in the stair-step waveform only having 4 steps up and down and the bottom step would be twice the width of all the other steps.

[@danielpintescu9486]

Hello! Can you put the proteus PCB schematic please ? I want it for that rotary switch. Thank you and great work!

[@scullcomhobbyelectronics1702]

Hi Daniel, I have some KiCad files for this project which you can download from the link below: www.scullcom.com/Stair_Step_Gen_KiCad_Files.zip If you unzip the folder you will have all the files. Regards, Louis

[@ovalwingnut]

👍😁 ❤ I haven't used "my Johnson" this much since I was of dating age 🤓 Thank you for a very through, information packed and interesting video. One question: The individual steps are for what purpose? I would assume scope linearity but the steps voltages could be set a little fast and loose if not paid attention too. Unlike the 5v overall, they can be (are) individually set. I ask because there is another commercial scope calibrator that uses steps also. Cheers! 🇺🇸❤🇬🇧

[@adilmalik7066]

amazing video as usual! really appreciate your work! I was wondering can you extend this into a Transistor Curve tracer?

[@scullcomhobbyelectronics1702]

Thanks. An interesting point you make about a Transistor Curve Tracer. Yes you could use the stair-step waveform to drive the base current of a transistor as part of a curve tracer. You would also need a voltage ramp waveform to drive the collector voltage of the transistor under test. You would also need some additional circuitry to drive the X and Y inputs of an oscilloscope to produce the correct traces.

[@pa4tim]

www.pa4tim.nl/?p=1437 forget the UJT staircase generator I used and use the design from Scullcom as a base. Just a minor thing to the staircase generator power supply. Regulators do not like a higher voltage on the output compared to the input and can die that way (caused by then electrolitic caps). To prevent that from happening you should place a diode over the regulator (see datasheet for details)

[@danycu100]

Hello! My counter gives the signals at the same moment of time not in a secvential way... any ideeas?

[@scullcomhobbyelectronics1702]

Hi Daniel. I am not sure what you mean? Regards, Louis

[@phillipalexander5389]

Skull com. What kind of swiches are there to use in circuits. And what are pulse circuits , and pulse. Switches.

[@scullcomhobbyelectronics1702]

Hi Phillip, The switches are: S1 - Rotary Switch, 6 Way, Through Hole - break before make type. (RS Components Ltd stock No. 665-196) Lorlin (Mfr. Part No. CK1050). SW2 - Single Pole ON-OFF-ON switch or 3 pin SIL option link with link plug You can download a parts list: www.scullcom.com/Stair_Step_Gen_Parts_List.pdf Regards, Louis

[@johndreyer4624]

While watching this it struck me that the 562 ohm resistor could be replaced with a 1N4148 to achieve the desired 0.6V voltage drop. Likewise the 1k ohm resistor can be replaced with two 1N4148 diodes in series; the 1k74 resistor with 3 x 1N4148 diodes in series; the 3k26 resistor with 4 x 1N4148 diodes in series and the 7k68 resistor with 5 x 1N4148 diodes in series. This will ensure that the steps of the waveform are of equal size; additionally there is no need to try and find non-standard resistor values. 1N4148 diodes are very cheap; the design uses 9 of these already.

[@kevy1yt]

Just for fun you should drop the input freq to around 1Khz or so and mess with all the controls while listening to the signal. Might be interesting.

[@scullcomhobbyelectronics1702]

Interesting! Could be worth trying!!

[@isidoromaich7226]

With every video in this channel I learn something new. I recently used a TTi Pulse Generator, it has many options! and is very simple and useful. Can you design something like that?

[@scullcomhobbyelectronics1702]

Thanks for your comments. I will have a look at a pulse generator project.

[@magedasd1045]

You have a great channel I really enjoyed this video! subscribed & liked excellent design & build tutorial I really need a circuit that can now the speed of a spark in the spark plug gap thanks

[@scullcomhobbyelectronics1702]

Thanks for you comment.

[@soldermaster4737]

Look at your schematic for this project, near the 74LS390 chips. There are two lines that go nowhere, please fix your schematic.I wish you would do a Mark2 version of this project using a Arduino Nano and solid state switches and a keypad to input any changes needed to control this great project. Take care.

[@SureshKumar-nk2ok]

my query help I not related to uploaded video on step generator

[@scullcomhobbyelectronics1702]

Checkout the TCXO tutorial at the link below: www.vectron.com/products/literature_library/tutorial_on_tcxos.pdf

[@SureshKumar-nk2ok]

sir pls upload TXCO using 20mhz XO for getting 10.000mhz signal output

[@SureshKumar-nk2ok]

recently I unsealed TXCO of 10.000mhz ,it contains 20mhz xo and two ic's PWM switching power controller. micro power voltage regulator . pls upload circuit sir related to it.

[@scullcomhobbyelectronics1702]

Were any of the IC's a HEF4046B in which case it the circuit would be a phase-locked loop circuit.

[@outofround]

I couldn't find an LTC1799 in a DIP package so I used a 555 timer for a clock.

[@SureshKumar-nk2ok]

any book written by you sir

[@scullcomhobbyelectronics1702]

Sorry no books. But you can checkout my website at: www.scullcom.uk

[@DeeegerD]

I didn't see anyone else ask so I will. What do you do with a stair step generator?

[@scullcomhobbyelectronics1702]

It could be used for a number of things such as as a simple check for oscilloscope scale calibration test. Also it could be used as part of a Transistor Curve Tracer circuit. You could also use it to test stepper motors. It could also be used to provide a video signal for a bar grey scale test pattern.

[@DeeegerD]

Scullcom Hobby Electronics Thanks

[@SureshKumar-nk2ok]

sorry sir, recently I teared down 10.000mhz TXCO of TELE QUARTZ manufactured ,I found crystal and associated circuit in smd components I required such kind of circuit.

[@SureshKumar-nk2ok]

thank you very much sir iam very much obliged to you sir. how can I become like you sir in designing many kinds of circuits.

[@scullcomhobbyelectronics1702]

Thanks you will learn over time - keep at it and you will do well.

[@andrewferg8737]

Hoping you can help me with some expert advice. Question: How would I modulated the individual stairsteps? I've been able to combine a modulated carrier and a stair step (kzbin.info/www/bejne/oKuYn6iKqrtmfM0 and kzbin.info/www/bejne/fHLblJaYpJeSZ7s ) but this just creates a PWM for the stair step. It creates groups of stairs. How can I add the high frequency modulation within each pyramid step?

[@bertoid]

Interesting project, but your calculations could have been simpler. Instead of working out the currents and doing two calculations for each voltage, you could do:- From the voltage divider formula: VO=VI(R2/(R1+R2)) And with: VI=4.4 and R2=1200 We get:- V=4.4(1200/(R+1200)) Rearranging... V=5280/(R+1200) VR+1200V=5280 VR=5280-1200V R=(5280-1200V)/V We get:- R=(5280/V)-1200 (not a huge saving for just 5 calcs, but a general principle. eg: You might want 10 steps...) And inserting the required Voltages:- V=0.6 => R=7600 V=1.2 => R=3200 V=1.8 => R=1733 V=2.4 => R=1000 V=3.0 => R=560 If one doesn't want to use 0.1% resistors, use two standard E12 values resistors where required:- 7k5+100R 2k2+1k 1k8||47k (=1733.6) Or 1620+113 (E96 1% values) from calculator at: www.qsl.net/in3otd/parallr.html 1k 560R

[@scullcomhobbyelectronics1702]

Thanks for the detailed info. I am sure it will be of help to others following. Regards, Louis

[@SureshKumar-nk2ok]

basically iam diploma in electronics with little known mathematics

[@andrewferg8737]

Spent Saturday afternoon at the workbench: kzbin.info/www/bejne/oKuYn6iKqrtmfM0 Works great for micro-stepping (with a few modifications). Thanks for sharing!!!

[@SureshKumar-nk2ok]

RESPECTED SIR PLEASE UPLOAD 10.000MHZ TCXO FOR REFERENCE CALIBRATION. REGARDS

[@scullcomhobbyelectronics1702]

Hi. Not sure what you mean. This project does not use a 10MHz TCXO.