| Electronics > Beginners |
| Hex Inverter OSC help. |
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| elizark:
Hey EEVblog! Total electronics noob here! Only been studying for almost a week now. Been following Dave for years but only recently got into electronics. I decided to follow casperelectronics' OSC tutorial (I'm a synth enthusiast) which only uses a CD40106BE IC, some capacitors, and some resistors/pots! I tried running the output directly to a little speaker I salvaged a while back, but found the oscillation would stop due after a short time to what I assume was the speaker drawing all the current from the IC that would cycle back through the capacitor (could be terrible wrong). I did some research and found that I was to use a buffer circuit. I had a TL074 quad op amp laying around so i slapped that on the breadboard and made a buffer to route the OSC into. Problem is, I'm not getting ANYTHING on the op amp output! Had me baffled and eventually defeated me for the night. If anyone could help me out it would be super appreciated!! As well as some tips to making this a VCO possibly? I'm planning on asking a lot on the forums here. CV, Exponential converters, low pass filters.... all of it I hope to make :D P.S. I'm not powering the op amp chip as I do not have a dual power supply. I have 9v batteries I could use to jank one up, but haven't yet. I'm fairly certain the reason it isn't working is because the op amp is not powered |O. I have tried hooking Vin+ to 9v and Vin- to GND, but still no luck. I know I should learn more about what I'm using but that's why I'm here! EDIT: Uploaded schematic. Vcc = 9v DC |
| spec:
Hi elizark Can you tell us about your loudspeaker? On your schematic it is shown as a buzzer which is quite different to a loudspeaker. If it is a loudspeaker can you tell us the impedance (resistance) of your loudspeaker. If the resistance is not marked on the loudspeaker you can measure it with a multimeter set to the low ohms range. The resistance should be in the range 3 Ohms to 32 Ohms. |
| elizark:
Cheers for the reply! I'm not at the shop ATM but I believe I read 8ohm on the back of it! I couldn't find anything but buzzers in the EasyEDA libraries. Sincere apologies! |
| Zero999:
Of course the op-amp must be powered to work. The TL074 doesn't have enough output current drive to power a speaker. You need a power audio amplifier IC. The LM386 is better suited to the job. |
| elizark:
--- Quote from: Zero999 on January 10, 2019, 09:01:41 am ---Of course the op-amp must be powered to work. The TL074 doesn't have enough output current drive to power a speaker. You need a power audio amplifier IC. The LM386 is better suited to the job. --- End quote --- I assumed that was the issue. Silly me! Even if I had powered the TL074 with +/- 9v would it not be enough? https://www.eecs.tufts.edu/~dsculley/tutorial/opamps/opamps5.html That link above is what I used to make the buffer. If I fed the buffer into another op amp and raised the gain using the equation from that link, would that drive enough current? The speaker I'm using now is from an old Panasonic cassette memo thing. I do plan on wiring a 1/4" jack to run it to a preamp, so would that eliminate the need for anything past the buffer? Sorry, I feel these are basic questions! I hope to learn a LOT from the community! :) |
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