Відео

Hi, thanks for the question. Two main reasons really:- 1) with your multimeter set to Resistance mode, you would be connecting an Output device to an Output device. 2) impedance is not just resistance. It's the combined opposition to current caused by resistance and reactance (capacitive and inductive). The effect of reactance can only be observed (or measured) when an AC current of the same operating frequency is passed through the circuitry. If you have not seen it already, I recommend you watch my "Impedance Explained" video, link below:- ua-cam.com/video/3QtpaICzSNc/v-deo.html

@@mattias99475 Brilliant! Thanks for your comment.

That's great to hear. Many thanks for your comment.

t1 is 0.693 x (Ra + Rb) * C. Ra is 10K or 10,000 and Rb is 100K or 100,000. Ra + Rb is therefore 110,000. 0.693 x 110,000 x 0.0000022 is 0.167 or 167mS. t2 is 0.693 x Rb x C. Rb is 100K or 100,000. 0.693 x 100,000 x 0.0000022 is 0.152 or 152mS. Hope this helps.

@ Silly me. Thank you so much.

Thanks for the comment, glad you enjoyed.

So very true. It's so much more rewarding if you develop solutions without resorting to software. Microcontrollers are amazing developments and certainly have their place. I also feel that a lot of young enthusiasts start out in the world of low cost microcontrollers and begin learning electronics from there.

Hi, yes that's an idea, I will add to the list. Thanks

😆

@@RobRoschewsk another big reason is reduced inventory. If they have one product that needs that part, the R&D teams will be encouraged to make as much use of it as possible.

BTW the company that supply the control board wanted over £270 for a replacement and wouldn't share the schematic to help either. I would estimate no more than £30 worth of components, including the PCB.

Exactly

You could, but remember the output will be a fixed duration. If the length of the switch press is important to your project, then you can still use the 555 as de-bounce, but in a different manner. See my "Switch De Bounce Using a 555 Timer Chip" video (link below):- ua-cam.com/video/mfoYkVQkLyc/v-deo.htmlsi=35hLxNfdUxvZ59md

Not quite sure what you mean. Presume you mean the additional unwanted resistance of the PCB and connectors?

Thanks. Glad you liked it and thanks for a great comment.

You use an extra resistor, an extra capacitor and a diode, all connected to the trigger pin. The capacitor goes between the extra resistor/push button and the trigger pin. The diode is there to limit the overshoot voltage to the NE555. The capacitor means that the trigger input only ever sees a pulse, never a constant voltage.

@Mark1024MAK thank you. I knew it wasn't an overly extravagant set-up

On the list.........

Glad you liked. Thanks for watching and many thanks for your comment.

Great! Keep watching :) Thanks for your comment.

Many thanks, glad you liked.

Glad you enjoyed and thanks for the comment. More videos coming and in the meantime there are many others already on my channel if you haven't already watched. This particular video took quite some effort to prepare, as did the 555 (It's Not A Timer) and Impedance (One Guy Missing) videos.

Thanks for the comment. I just use PowerPoint, nothing fancy. Also I prep a lot of the images with Gimp and utilise several Web services such as Canva.

@@paulpkae Thanks - I have GIMP and Libre Office equivalent to PowerPoint. Not familiar with Canva but I'll check it out.

Hi, thanks for your comment. Audio is a complex topic with many aspects that can affect your perceived level of sound intensity. Impedance matching may well be one of them, but as you are probably aware, the human ear (and brain) perceives loudness in varying scales across the hearing frequency range and to make it more complicated, your amplifier/speaker arrangement will not produce an entirely flat frequency response either. Back in the day, old amplifiers used to have a LOUDNESS button which simply boosted the low frequency component of the audio signal, tricking the brain into thinking the music was much louder than it really was. It looks like you have some great HiFi kit there, so I would be careful about tinkering around too much. If anything, I would suggest measuring the actual impedance of your speaker/cable arrangement with an impedance meter. 1khz is critical for speech intelligibility, but for music you should probably check across the hearing frequency range (each octave) and see what you get. My background is Public Address systems so although I understand audio, I'm no HiFi expert. There may be other viewers on this channel that can help further.

@@paulpkae thanks for the response!! I've been reading up on all this. I think you're right on testing out the impedance across the frequency range of the speaker crossover and cabling, so see what the top and bottom would be. I just got a cheapo oscilloscope too, and plan on doing SUPER basic testing and measuring. It's interesting to find that there are speaker cables specifically made to show more impedance, or capacitance, etc.

Glad you found it useful and many thanks for your comment, much appreciated.

That's great! Thanks for your comment.

The pot value will affect the frequency of the output but does not necessarily need to be similar to Ra or Rb. It's essential that Ra is of a reasonable size to prevent too much current flowing from the positive rail through the Discharge transistor to ground.

@@paulpkae Thank you!

Hi, thanks for Subscribing, First of all, the 555 can be powered from 12V supply and will give you a 12V output (or very near to 12v). You will probably need to hang a transistor off of the 555 in order to support the current of your fan. With regard to turning off in relation to your PWM signal, I don't quite understand the arrangement/what's required. Is the PWM driving the fan, if not what is it driving. Are you looking to detect when the PWM signal stops, and then stop the fan 20-30 seconds after that, or looking to detect the PWM has stopped for at least 20seconds before turning the fan off?

@paulpkae thanks for your help. This is a cooling fan on a small laser diode. 12v to the fan is always on. The pwm signal fires the laser beam. So trying to stop the fan running as it's very loud after the pwm signal has stopped for 20 to 30 seconds to allow the laser to cool down. Meaning the laser had finished it's lasers job, the module as cooled down, so now turn the fan off. When pwn signal comes back on the next laser job, the fan starts again. The 12v, ground and pwm is all in the same 3 core cable

@@FlixmyswitchLASER OK. I think you can arrange a simple circuit to do this with an Op-amp, diode, transistor, capacitor and a couple of resistors. If you configure an op-amp as a voltage follower with a diode within the loop back (see my "All About Op-Amps" video, "Perfect Diode" section 11:07), then connect + terminal of a capacitor to the output & - to GND, the capacitor will act as a peak detector to whatever signal is fed into the non-inverting input (which will be your PWM signal). By using an op-amp there will be no additional load pulling down your PWM. You will need to add a blead resistor in parallel with the cap so that it has a discharge route when the PWM signal stops (something large 100K+). Now connect another resistor from the +terminal of the cap and into the Base of an NPN transistor. 12V+ to one side of your fan, then the negative side of the fan onto the Collector of the transistor and the Emitter to GND. While the PWM is running the capacitor charge is regularly being topped up and will experience minimal discharge between cycles. The charge keeps the transistor switched ON and allowing current to pass through the fan to GND. When the PWM stops, the cap will discharge through the blead resistor and Base/Emitter junction and eventually the transistor will turn OFF. You will need to play around with the resistor and capacitor values a little. I will do a little sketch later and give you a link to download, should make it easier to follow. Hope it helps.....

@paulpkae thanks time to do some study

@paulpkae thanks for your detailed reply. If you are able to produce a sketch that would be very helpful

Thanks for your comment, much appreciated.

Thanks very much, glad you enjoyed it.

Thank you, glad you enjoyed.

"My friends, as I have discovered myself, there are no disasters, only opportunities. And, indeed, opportunities for fresh disasters."

Quite possibly :)

Many thanks for your comment. I never really learnt much from school. It was only after being exposed to real world situations that I became interested in certain topics and was then highly driven to learn.

Many thanks, much appreciated.

Many thanks. There are countless iterations of the 555 circuits out there and some have been stretched well beyond what people thought possible. Like all electronic components and ICs, they are just the building blocks for us to play around with and create all sorts of configurations.

That's great to hear. Thanks for the comment and thanks for Subscribing too.

Thanks for your comment. My heat gun is still going strong, used regularly and I can honestly say that model is great quality for the price.

Hi, thanks for the comment. That video felt like a 100 mile an hour run through so much stuff it was not really feasible to delve to much into each aspect and circuit. I do intend doing a follow up video whilst putting together an audio mixer project for my office. A lot more detail will be given in that. Watch this space..... 🙂

Many thanks.

Thank you. More videos coming......

Hope you enjoyed this one then :) . Thanks for watching and thanks for the comment.

Glad it helped.

That's great to hear. More videos coming......

Hi, thanks for the comment. I have just uploaded the spreadsheet and you can now download it from here:- 1drv.ms/f/c/10f323cd9840b5df/EknQIwciMO1NnKcfaTDeZZQBiHeleHQV0ED1RoaRtsEXzw?e=HF4PbV

Thank you so much. I'm really grateful.