Electronics > Beginners
Hex Inverter OSC help.
L_Euler:
In addition to above suggestions, you may want to consider using a couple more of those inverters to further isolate your oscillator. Output of A into B. Output of B into C. A transistor on the output of that op amp would help too. See attached
spec:
--- Quote from: elizark on January 10, 2019, 09:05:40 pm ---
--- Quote from: spec on January 10, 2019, 12:15:27 pm ---+ elizark
Attached is a schematic for a circuit, using the CD40106 and a couple of transistors, to generate an audio tone from 100Hz to 10KHz. If you have any questions just ask. :)
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Hey spec! Thanks for this circuit! Might as well give it a try and try to learn as much as I can from it :D
To stop bumping this thread should I ask questions about it in PM?
Cheers!
--- End quote ---
No probs elizark
No, just ask away in open forum that will be fine (I get inundated with PM requests for assistance and am afraid that I simply cannot handle them all) :)
Yes, if you build the circuit of reply #6 and get that working, it will be a good step forward and I suggest good experience . We can then possibly modify it for a better sound, if you want. But, quite honestly, there are much better approaches than using a CD40106 chip.
If you are wondering about the five Schmidt inverters in parallel, they isolate the oscillator from the output and together provide sufficient current to drive the output transistors. The CD40106 chip, being a low power CMOS type, does not have much current drive capability.
As you are intending to develop a more advanced synth, perhaps you could work on a description and specification of what you want. The highest level decision is whether to use a microcontroller or not.
Also, what will the power supply be?
spec:
--- Quote from: elizark on January 10, 2019, 09:03:45 pm ---The dreaded datasheet! Still a bit scared of those...
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Datasheets can look a bit daunting at first, but they are your best friend in electronics and, when you get familiar with them, they are not that hard. Remember that some of the stuff on a datasheet is either boiler-plate or bull. And a lot of the data is simply not needed for the majority of applications.
If you are planning on getting into electronics you must get with datasheets and learn the important parameters for each device type that you would need for normal designs. For example, with opamps, you only need the following parameters:
* Supply lines max and min
* Input voltage range
* Input offset voltage
* Input bias current
* Output voltage swing
* Output current capability
* Frequency response Also, from the literally thousands of component types available, you only need to stock and know about a relatively few common types to cover most applications. For example, one of the most widely used twin opamps is the LM358. But my goto opamps are the TX711/TX712 and OPA192/OPA2192. The other thing is that many components with different type numbers are either identical or so close that it makes little difference in practice. This is especially the case with BJTs. For example, there are many equivalents to the BC337.
This is my list of complementary goto jellybean bipolar junction transistors (BJTs):
BC546C/BC556C : 65V, 100mA, 500mW, TO92
BC337-40/BC327-40 : 45V, 500mA, 625mW, TO92
TIP41C/TIP42C : 100V, 6A, 65W, 2degCW, 150degC TO220
TIP35C/TIP36C : 100V, 25A, 125W, 1degCW, 150degC TO247
2N3055/MJ2955 : 70V, 15A, 115W, 1.52degCW, 200degC, TO3
Note that this is just my goto list, others will have their own lists. But the important thing is to have a list so that you are not swimming around in a sea of different types.
Of course you will need specialist components but, if you have a solid base of goto components, you can concentrate on learning about the specialist components, without having to worry about the fundamental goto components. For example when designing, the circuit of reply #6, I didn't need to search for a suitable complementary transistor pair. I just dropped in the BC337/BC327s. And if more power were required, just use the TIP41/TIP42s pair from the goto list.
This whole area is part of design (not just electronic) and is known as variety reduction (VR). To take an example you may do a design and calculate that you need a 10nF capacitor here, a 12nF capacitor there and a 70nF capacitor somewhere else. So what you would do is just fit 100nF (goto value) capacitors in all locations. Naturally, some components must have absolute values, the oscillator timing capacitor in reply#6 schematic for example, but in many cases the calculated capacitor values are for minimum values.
elizark:
spec
--- Quote from: spec on January 11, 2019, 12:21:38 am --- No probs elizark
No, just ask away in open forum that will be fine (I get inundated with PM requests for assistance and am afraid that I simply cannot handle them all) :)
Yes, if you build the circuit of reply #6 and get that working, it will be a good step forward and I suggest good experience . We can then possibly modify it for a better sound, if you want. But, quite honestly, there are much better approaches than using a CD40106 chip.
If you are wondering about the five Schmidt inverters in parallel, they isolate the oscillator from the output and together provide sufficient current to drive the output transistors. The CD40106 chip, being a low power CMOS type, does not have much current drive capability.
As you are intending to develop a more advanced synth, perhaps you could work on a description and specification of what you want. The highest level decision is whether to use a microcontroller or not.
Also, what will the power supply be?
--- End quote ---
I have been wanting to build my own modular synth rig for ages now and am only now taking action to attempt to learn electronics. I've gotten a grasp of the molecular level stuff, just not the practical stuff. I plan to go to school to major in electronic engineering since electronics have always fascinated me for my whole life really. If possible I'd want to keep it fully analogue, except for a CV to MIDI module. I've thought about DIY module kits, but I really like to learn EVERYTHING of whats going on in the synths (it just takes me some time to grasp). There is a Youtuber "LOOK MUM NO COMPUTER" who makes his own modules, and even makes tutorials on some, but they are pretty hard to follow. His videos were the main push for me to actually start getting hands on (and Dave's 2 min teardowns of course!). Power supply would probably be +/- 18v but I don't know why, I've just heard that somewhere.
I was wondering about why those would be in parallel! By isolate the oscillator from the output, how do you mean? As in act as the buffer? And what do the transistors do exactly? Not SUPER keen on transistors but know the basics, like switching transistors.
--- Quote from: spec on January 11, 2019, 01:31:19 am ---
--- Quote from: elizark on January 10, 2019, 09:03:45 pm ---The dreaded datasheet! Still a bit scared of those...
--- End quote ---
Datasheets can look a bit daunting at first, but they are your best friend in electronics and, when you get familiar with them, they are not that hard. Remember that some of the stuff on a datasheet is either boiler-plate or bull.
If you are planning on getting into electronics you must get with datasheets and learn the important parameters for each device type that you would need for normal designs. For example, with opamps, you only need the following parameters:
* Supply lines max and min
* Input voltage range
* Input offset voltage
* Input bias current
* Output voltage swing
* Output current capability
* Frequency response Also, from the literally thousands of component types available, you only need to stock and know about a relatively few common types. For example, one of the most widely used twin opamps is the LM358. But my goto opamps are the TX711/TX712 and OPA192/OPA2192.
This is my list of complementary goto jellybean bipolar junction transistors (BJTs):
BC546C/BC556C : 65V, 100mA, 500mW, TO92
BC337-40/BC327-40 : 45V, 500mA, 625mW, TO92
TIP41C/TIP42C : 100V, 6A, 65W, 2degCW, 150degC TO220
TIP35C/TIP36C : 100V, 25A, 125W, 1degCW, 150degC TO247
2N3055/MJ2955 : 70V, 15A, 115W, 1.52degCW, 200degC, TO3
--- End quote ---
Thanks for this! Definitely adding this to the notes.
spec:
--- Quote from: elizark on January 11, 2019, 03:16:37 am ---
I have been wanting to build my own modular synth rig for ages now and am only now taking action to attempt to learn electronics. I've gotten a grasp of the molecular level stuff, just not the practical stuff. I plan to go to school to major in electronic engineering since electronics have always fascinated me for my whole life really.
--- End quote ---
That is a fundamentally important area that you have already got but, from what you say, you have a long learning program ahead.
--- Quote from: elizark on January 11, 2019, 03:16:37 am ---If possible I'd want to keep it fully analogue, except for a CV to MIDI module. I've thought about DIY module kits, but I really like to learn EVERYTHING of whats going on in the synths (it just takes me some time to grasp). There is a Youtuber "LOOK MUM NO COMPUTER" who makes his own modules, and even makes tutorials on some, but they are pretty hard to follow. His videos were the main push for me to actually start getting hands on (and Dave's 2 min teardowns of course!).
--- End quote ---
OK analogue it is.
--- Quote from: elizark on January 11, 2019, 03:16:37 am ---Power supply would probably be +/- 18v but I don't know why, I've just heard that somewhere.
--- End quote ---
+-18V is often used for high-end audio pre amplifier stages because it gives the largest dynamic range while still staying within the maximum recommended operating voltage of good sounding audio opamps. Will the PSU be mains powered or battery powered or both?
--- Quote from: elizark on January 11, 2019, 03:16:37 am ---I was wondering about why those would be in parallel! By isolate the oscillator from the output, how do you mean? As in act as the buffer? And what do the transistors do exactly?
--- End quote ---
Yes, act as buffers so that N1A can get on with its job of oscillating without being affected by the relatively high current of the loudspeaker. The decoupling capacitors help in this too. The combined output from the buffers is around +- 5mA which would not be able to make much volume in the loudspeaker, so the transistors provide more current. Typically BC337/327 would have a current gain (emitter current/base current in this case) of around 100 in that configuration, so that the current available to the speaker would be 5mA * 100 = 500mA. Note that current gain of a BJT is known as HFE and is formally, collector current/base current.
But 500mA would be very loud (and there is no volume control) and would soon flatten your 9V battery. The resistor in series with the speaker limits the speaker current to +-75mA.
The output at the two transistor emitters will be a square wave of between 1V and 8V which would not be suitable for the speaker. The capacitor in series with the speaker therefore changes this to a square wave of -3V5 to +3V5, which has no DC content and is thus suitable for the speaker.
--- Quote from: elizark on January 11, 2019, 03:16:37 am ---Not SUPER keen on transistors but know the basics, like switching transistors.
--- End quote ---
Afraid that transistors, both BJTs and MOSFETs are the essential active elements of modern electronics. By the way, although transistors can be used as switches, and there are transistors specifically designed for switching, all transistors are analogue.
Every integrated circuit, both analogue and digital, is made from transistors, sometimes billions of them. Along with resistors, capacitors, inductors, transformers, and diodes, you need to fully understand how both types of transistor work at the essential level. The good news is that it is not difficult. :)
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