Turntable Stroboscope
 

Split from this thread: https://www.vintage-radio.net/forum/...d.php?t=152165

All this talk of oscillators and crystals reminded me that I've still to design and build a 300Hz strobe to help with adjusting my turntable(s) speed of rotation.

I know it's slightly off-topic but thought that something might have cropped in the Chinese AM radio kits arena - or if anyone would like to assist??

Re: More Chinese AM radio kits
 

300Hz strobe: Start with a common 2.457600MHz baud rate crystal, and divide it with a ripple counter down to 300Hz.

The easiest way to do that would be to use a single CMOS 4060 IC as both crystal oscillator and counter. The 300Hz output would be from pin 2 (divide by 8192), I think. Use that output to drive a LED on and off via a transistor.

Re: More Chinese AM radio kits
 

Some time ago I made a 100/120 flashes/second strobe. Started from a 4.9...MHz crystal oscillator module, then 3 common 74HCT chips. Drives 4 white LEDs. I built it for setting the spindle speed on old floppy disk drives (which had a strobe disk on the spindle pulley) and it was easily good enough for that and gives one of the clearest stationary patterns I have ever seen.

Of course the 2 flash rates let me use strobe disks either intended for 50Hz or 60Hz lighting.

I can provide the circuit diagram if anyone wants it.

Re: More Chinese AM radio kits
 

Thanks Sirius and Tony

My circuit design skills are woefully lacking so any assistance whatsoever in this department would be extremely helpful. Always keen to learn, even at my age!

Re: Turntable Stroboscope
 

I got one of these https://www.ebay.co.uk/itm/1Hz-65534...YAAOSwQ5pb9pO3 for a work test jig, works well. A LED would work direct from the output.

Re: Turntable Stroboscope
 

I've attached a scan of my circuit (sorry, I don't use CAD, I use a 'paper aided design' system, better known as a pad).

A couple of things : I've not shown the power and ground connections to the ICs, they go to +5V (output of the 7805) and ground. Also add a 100nF disk ceramic capacitor between +5V and ground close to each IC (that is probably overkill when it comes to decoupling but such capacitors are a lot cheaper than my debugging time, at least for a one-off).

The thing runs off a 12v wall-wart type power supply.

There is a 2-pole 3-way switch. Centre position is off. Flipped one way you get 100 flashes/second. The other way you get 120.

The LEDs are on for 1/16th of the time. A short flash (rather than 50:50 on/off ratio) gives a clearer 'still' pattern of the strobe disk.

You are welcome to make this non-commerically. If you start selling them then I feel I deserve something in return.

Re: Turntable Stroboscope
 

Sounds like a good Arduino project. An attiny85 (8 pin chip) and an LED might be all you need assuming it can run an output at 300 Hz with the Arduino code overhead. Should be a simple programme. If I have time this weekend I'll test that for you and report back.

Re: Turntable Stroboscope
 

Yes that works with attiny 85. I tested it using the attiny's built in oscillator but you would probably want to use an external xtal for stability. There is also the possbility to programme a few selectable frequencies if tou want. If you are not familiar with programming Arduino's (lots of good tutorials on youtube) then I would be happy to program the chip for you. Programme (sketch) below. Assumes an led is connected to pin 7 via a suitable resistor.

/*
Strobe at 300Hz

LED connect from pin 7 to ground via suitable current limit resistor
*/
int LED = 1; // PB1 maps to pin 6 on attiny85
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
digitalWrite(LED, HIGH); // turn the LED on (HIGH is the voltage level)
delayMicroseconds (333); // delay 333 uS
digitalWrite(LED, LOW); // turn the LED off by making the voltage LOW
delayMicroseconds (3000); // delay 3000 uS

}

Re: Turntable Stroboscope
 

Ian's method is the way to go if you happen to have an Arduino on hand as the hardware is built for you, even down to there being an LED already on the PCB.

If you prefer a basic electronic circuit, this 4060 oscillator / divider (attached, from the internet), might be a good starting point. The output you'd need to use for 300Hz would be from pin 2, and you'd have to use that to drive a transistor or darlington pair, in turn driving an LED.

Re: Turntable Stroboscope
 

Wow - thanks guys but unfortunately a bit beyond my knowledge and understanding" :dunce:

What I really need now is to find a Ladybird "Guide to Oscillators and Crystals", a Look and Learn "Oscillator/Dividers/Counters" supplement but appreciate I've no chance of sourcing an Eagle Annual cutaway drawing explaining "How a CMOS 4060 IC works"! :)

These days it's all "Idiots Guides .. " !

Looks like more R&D is needed on my part so I'll get onto this Project in the New Year.

Meantime best wishes to everyone for the Festive Period and for a prosperous New Year. ;D

Re: Turntable Stroboscope
 

The circuit shows the crystal oscillator bits (the active bits are inside the chip).

The 4060 itself is simply an oscillator and a string of 14 binary dividers with most of the intermediate divider stage outputs brought out to pins. It's very useful for producing long, reasonably accurate time delays without resorting to gigohm and farad RC circuits 8-)

Re: Turntable Stroboscope
 

Happy New Year to all on the Forum.

Getting back on track with my planned 300 Hz strobe I managed to borrow a "commercial" product from a friend and took pictures of the board and components - many unmarked!

It's based on a 4.9152 crystal and an HEF4060BP binary counter/divider and oscillator.

What's the easiest way to reverse engineer a circuit diagram from a picture of a board - I'd like to understand what is going on rather than just lash up a DIY copy.

I'll probably need some help in identifying the value and type of certain components further down the line but meantime can anyone identify the diodes in the attached pictures - I can't see any markings?

Re: Turntable Stroboscope
 

Probably silicon general purpose diodes, 1N914 or 1N4148

Peter

Re: Turntable Stroboscope
 

Looking for a bit more technical assistance as I try to educate myself on how Oscillators and Crystals work in a circuit.

As mentioned above I'm trying to construct a 300 Hz strobe based around a 4.9152 crystal and an HEF4060BP binary counter/divider and oscillator. Looking at the Product data sheet for the HEF4060BP we have the Pin out diagram : -

Attachment 176570

I'm confused by how you calculate the counter out values when there is no Q1, Q2 or Q10 - see here for the Pin description table: -

Attachment 176571

To get from 4915200 Hz to 300 Hz I need to divide by 2 ^14 i.e. 16384 - so, put simply, what pin would that be??

I appreciate I need to build a circuit involving caps and resistors to get the whole thing oscillating and that a Darlington pair will be required to drive an LED - I'll also need some judiciously place diodes.

Small steps ...

Re: Turntable Stroboscope
 

Use Q13, it starts at Q0 so that is 14 in real money. Funnily enough I recommended this chip to a work colleague a few days ago for a time out function, my brain sucked it out of the dim and distant past.
The datasheet gives the circuit for crystal use, a couple of caps and a resistor. If you run it from 5V (three 1.5V cells is good) it will drive a white LED directly, no resistor or transistor needed. Modern LEDs are very bright and the chip won't mind.

Re: Turntable Stroboscope
 

This data sheet should clear the confusion:

https://pdf1.alldatasheet.com/datash...HEF4060BP.html

Lawrence.

Re: Turntable Stroboscope
 

Thanks - makes perfect sense now that I know it starts at Q0 - so that's pin 3 on the HEF4060BP!

The circuit I was working on runs from a 9V battery and includes a Darlington pair, several resistors and capacitors, including electrolytics, along with some diodes to prevent back voltage. Something based on this: -

Attachment 176579

Your solution sounds much simpler to the extent that I may build both just out of curiosity and my own further education.

Re: Turntable Stroboscope
 

It will be unusual for any stock crystal to be unaffected by the circuit loading, so you can
replace one of the 22pF caps with a 66pF trimmer, and that will enable fine frequency
adjustment, when measured with a frequency meter. It also allows junk box crystals
to be pulled to the desired output.

Re: Turntable Stroboscope
 

Your output circuit is far too complicated. Use a 1k resistor to the base, (no capacitor), use a simple transistor with emitter connected to ground, put the LED in series with the collector resistor. If you need a lot of current use a n channel FET, there is plenty of voltage to drive it.
No diodes are needed but a capacitor across the chip power supply would be good.

White LEDs use fluorescence, I do not know whether they have a long time constant

Re: Turntable Stroboscope
 

Would this one be appropriate - seems a bit expensive: -

https://www.cricklewoodelectronics.com/CTR80908003.html

The circuit in the Product data sheet for the HEF4060BP shows a bias Resistor with the values 100 kΩ to 1 MΩ - should this be a variable Resistor?

Attachment 176626

Re: Turntable Stroboscope
 

65pF Vishay ones here for £2.44 + £1.38 p&p from a UK supplier:

https://www.ebay.co.uk/itm/Miniature...8YQQ:rk:7:pf:0

Hope that helps.

Re: Turntable Stroboscope
 

The circuit in the Product data sheet for the HEF4060BP shows a bias Resistor with the values 100 kΩ to 1 MΩ - should this be a variable Resistor?

No, the resistor is there to provide bias to get the input into a conductive region. Anything in the quoted range will do.

Re: Turntable Stroboscope
 

Thanks David - that's more like it.

Understood - thanks.

Re: Turntable Stroboscope
 

No, it means anything twixt 100k and 1M. I wouldn't bother with a trimmer 22p on it's own will do.

Re: Turntable Stroboscope
 

After a somewhat lengthy diversion to build a Raspberry Pi Wireless Print Server, now deployed and working, I'm back to looking at the 300Hz strobe.

I carefully followed the design for a Typical crystal oscillator circuit shown in the HEF4060B Product data sheet (page 8) and wired up all the required components on a Breadboard - see attached picture.

Couple of questions though: -

1. Will 4.5V be enough to get the whole thing oscillating?

2. How will I know that it is working at this stage before I go any further?

Thanks in advance...

Attachment 178130

Re: Turntable Stroboscope
 

1 Yes.
2 All outputs will measure about half Vdd.

Re: Turntable Stroboscope
 

If you have a 'scope, logic probe or logic analyser you can check the the outputs are oscillating (the first and last will also let you check the frequency).

Or a piezo buzzer (the passive type, not the type with internal electronics) connected between the '300Hz' output and ground will buzz at, not surprisingly, 300Hz. Now I can't judge pitch at all but even I can tell if it's oscillating.

Re: Turntable Stroboscope
 

For a lower price than the trimmer you can buy an entire crystal oscillator set accurate to within 50 parts per million ( 0.005%) runs on 5v

https://uk.farnell.com/qantek-techno...lator%204.9152

David

Re: Turntable Stroboscope
 

Using my Topward Digital Function Generator 8112 I'm getting widely fluctuating frequency signals (830Hz to 620Hz) which won't settle down even after allowing the unit to warm up and stabilise - some instability somewhere?

In addition the HEF4060BP started to run very hot - too hot to touch - so there may be something wrong with my Breadboard circuit connections??

I've incorporated a 4.9152 MHz crystal in the circuit I am using from the HEF4060B Product data sheet (page 8) - not sure how the component you provide a link for works?

Attachment 178152

Re: Turntable Stroboscope
 

What have you done with pin 12 of the 4060? It should be connected to 0V (pin 8) I think.

You are not using the Topward generator to feed a signal _into_ the 4060 I trust. That could cause the IC to overheat or damage said IC. You want to just monitor the signals coming from the IC.

Re: Turntable Stroboscope
 

Pin 12 is connected to Pin 8 which goes to GND.

On the Topward I'm using the COUNTER IN connection with the FUNC/COUNT button pressed in which shows the input frequency.

Re: Turntable Stroboscope
 

OK, that sounds right for pin 12.

Does the IC still overheat if the Topward (counter) is not connected?

You have the oscillator wired as in the datasheet. Pin 12 is grounded. You have a 4.5V battery between ground (pin 8) and pin 16. Are there any other connections to any pins of the IC?

Re: Turntable Stroboscope
 

I'll check for overheating with the Topward disconnected.

Pin 8 (Vss) and Pin 12 (MR) as detailed above

Pin 10 (RTC oscillator pin) and Pin 11 (RS clock input/oscillator pin) as per datasheet.

Connection from the battery to Pin 16 (Vdd)

Re: Turntable Stroboscope
 

It's a complete crystal and oscillator circuit in one package with an accuracy spec that encompasses the whole thing. Logic level outputs, so you power it from 5v and feed its output into pin 11 of the 4060. don't fir the rest of your oscillator circuit and leave pin 12 not connected to anything.

Excess heat in a CMOS logic part means something is either running at high frequency or is stuck between logic levels where the thing tries to operate in an analogue way and can waste current from the supply down through two transistors to ground. This makes heat.

I'd suspect spurious oscillation of some sort.

David

Re: Turntable Stroboscope
 

It's diffiicult to be sure, even in the enhanced photo of the breadboard below, but the oscillator components don't seem to be connected as per the circuit?

The resistor from pin 11 doesn't appear connected at the left hand end ?

The crystal appears to be connected across the trimmer ?

One end of the cap isn't connected at all?

As for the overheating - the +ve and -ve rails are connected to the opposite labelled busbars. - Not a problem unless you connect the battery as per the labels. That would likely get the chip hot!

Attachment 178170

Cheers

Re: Turntable Stroboscope
 

Thanks Trigon - oh dear, it's back to the Remedial Class for me!!!!

I note that "The resistor from pin 11 doesn't appear connected at the left hand end" and "One end of the cap isn't connected at all" - I'm assuming that this is one and the same missing link on the Breadboard?

Attachment 178218

"The crystal appears to be connected across the trimmer" - I'll look more closely at this but my understanding(!) is that only two tabs on the trimmer need to be connected - one of the outer tabs and the central tab?

As for the +ve and -ve rails hopefully I've got that right where the red denotes the positive (+) terminal, and black denotes the negative (-) terminal on the battery. I changed this slightly and had the red (+) terminal going straight to Pin 16 (Vdd). Nothing else on the board needs power.

The HEF4060B was running very hot so what are the chances it is fried?

Re: Turntable Stroboscope
 

Even if linked it doesn't correspond to the circuit - the junction between that resistor and capacitor should also be joined to the crystal.

One wire from each end of the crystal appears to go to some point on the trimmer, presumably not the same point, hence my 'connected across the trimmer'. Note that the crystal is not connected across the trimmer in the circuit diagram...

Pin 16 (+V) is pictured connected to a blue '-' rail, and pin 8 (0v) is connected to a red '+' rail, both with red jumpers. As I said it doesn't really matter unless you forget they're swapped and connect the battery to the rails as labeled.

Cheers

Re: Turntable Stroboscope
 

Thanks again Trigon for taking the time and effort to provide such detailed responses - much appreciated.

Translating circuit diagrams to actual layouts and wiring connections (and vice versa) in various restoration projects was never my strong point! Probably just need more practice but that is sometimes difficult with this hobby which is quite often put on hold for long periods of time due to other priorities.

What I think I'll do is take the old fashioned approach and use some coloured pencils to mock up my circuit on a paper Breadboard template.

I can then Post that here for advice, guidance and entertainment!!! :)

Re: Turntable Stroboscope
 

The HEF4060B is getting hard to find - anyone know a good (UK?) source or a modern equivalent?

Re: Turntable Stroboscope
 

If you search for 4060 in Google and select shopping there are loads. As you are running at 4.5V even the HC and HCT series will do.

Re: Turntable Stroboscope
 

Are all the prefixes and suffixes just designed to confuse someone like me??

I think this looks o.k. to me: -

https://uk.farnell.com/texas-instrum...07?st=CD4060BE

Re: Turntable Stroboscope
 

That would be fine.

The first two letters are of no significance - they just denote the maker.

For example, CD is RCA, MC is Motorola, SN is Texas Instruments.

Note however that while those from Farnell are cheap, they're US stock so you get caught with £15.95 delivery charge.

Re: Turntable Stroboscope
 

Noted David, thanks.

Managed to find some on eBay from a UK supplier.

Re: Turntable Stroboscope
 

I've replaced the 4060 along with the 4.9152 MHz crystal just in case that was fried as well.

Rewired my Breadboard circuit with shorter leads and paying much more attention to detail (thanks Trigon) - everything oscillating nicely but not quite the stability I need.

Still some fluctuation (+ - 10-20 Hz) which I assume could be being caused by some back voltage?

Would some judiciously placed diodes help in this instance?

I'm just doing this for my own education and interest (or stubbornness!) as I've also acquired the QX14T50B4.915200B50TT to try out as recommended by Radio Wrangler.

Re: Turntable Stroboscope
 

I had a go at making a strobe but in a senior moment designed it to give 50 or 60Hz square wave to drive a high brightness LED. When it did not work against a standard stroboscope disc the light came on in my head and I converted it to 100 or 120 Hz operation. :D
It was easy to do by re-selecting the LOAD inputs of the CD40103.
So the 4060 produces 2400Hz from the 2.4576MHz xtal, trimmed to give correct frequency. It runs from its own regulated 5V supply, the rest of the circuit uses the full 9V. Though it works fine, I failed to realise, as suggested in earlier post, that a shorter pulse would improve viewing on a strobe disc. That would probably make the CD4013 unnecessary and the 40103 could then be made to provide the 100/120Hz by making it divide by 24, (actual required load word 00010111 (23) and divide by 20, (actual required load word 00010011 (19) so only load bit J2 needs switching. Not tried that as the present illumination is OK for me. :D

Re: Turntable Stroboscope
 

After many false starts and abandoned trials I finally have a circuit oscillating at exactly 300 Hz - apologies for the shaky camera work: -

https://www.youtube.com/watch?v=7doS...ature=youtu.be

Thanks to Radio Wrangler (David) who encouraged me down the route of using a Qantek QX14T50B4.915200B50TT oscillator.

Next step is to replace the HEF4060B with a 74HC4060.

After that it's looking at the output waveform on my 'scope and what I need in the circuit to drive an LED i.e. get my head round Tony Duell's comments in Post #6 above and all that stuff to do with "persistence"!

A general thanks to Forum members for their ongoing support ...

Re: Turntable Stroboscope
 

"After that it's looking at the output waveform on my 'scope ... " - now there's a phrase that's easy to type but proving extremely challenging with my ageing Farnell 30-4D oscilloscope (rebadged Scopex 4D25 or Racal 9386 ?)

Any help would be appreciated ...

Re: Turntable Stroboscope
 

As to 'persistence' Tony Duel made a good point in post #6 regarding his (quite involved) circuit. Namely:

"The LEDs are on for 1/16th of the time. A short flash (rather than 50:50 on/off ratio) gives a clearer 'still' pattern of the strobe disk".

With an asymmetrical square wave, the LED is on for a shorter time than with a symmetrical square wave, so the flash period of the LED is shorter. Hence, if the LED has some ‘persistence’ rather than go straight off, it fades till the next ‘on’ period, so at 300 HZ might not seem to go off at all but may appear both to the naked eye and the strobe disc as a continuous light. To cite Tony's circuit, the LED would be on for only 6.25% of each cycle, and off for 92.75% so the flash would be more clearly defined, rather than a symmetrical square wave which would be high for 50% of each cycle, and low for 50%.

We know that LEDs quite unlike incandescent light bulbs in which a filament glows and take time to heat up and cool down. What isn't known, is to what extent say ultra-bright low current LEDs have 'persistence', and the only way of knowing that is to try one on a normal 50:50 square wave 300Hz signal.

As to your scope, you've said that you now have a stable 300Hz signal from your oscillator circuit, so if you feed that into the 'Y' input of your scope it should have do difficulty in displaying that to enable you to see the waveform, and the voltage. Don't know if the output of the oscillator would be high enough voltage to drive a low current ultra bright LED directly. Again, the only way of knowing is to try one.

What we do know for certain, is your own undoubted 'persistence' as amply demonstrated both with this project, and with the 'basket case' Bush AC91, which you persevered with until it behaved itself, long after many would have become disheartened and thrown in the towel!

Good luck with the project.

Hope that helps a bit.

Re: Turntable Stroboscope
 

Thanks David G4EBT for your ongoing encouragement, support and off-line mentoring - it really helps.

My Farnell oscilloscope (a rebadged Scopex 4D25?) was bought from another Forum member a few years ago but has never seen active service until now. It's fairly tatty and some of the front panel text was missing and replaced manually!! Of course I'd rather be using an oscilloscope than having to repair this one!

A few of the knobs feel as if they are slipping and I'm not sure if the trigger is working correctly? I'll be happier when I can see a waveform on the screen.

I'm quite pleased though that even at my age I'm still able to ask "daft boy" questions like "Where is the 'Y' input on my 'scope" - see image below.

Attachment 180180

Re: Turntable Stroboscope
 

Y is vertical axis, X is horizontal axis.

So Y in = Vertical, use A Vertical (BNC socket) and trigger from that channel.

Lawrence.