Problem creating a simple Triangle Wave oscillator

Thread Starter

skullkid2802

Joined Feb 1, 2019
6
Hello, I am fairly new to electronics besides having to solder an electric guitar's pickup wires. I recently have been trying to research some fun electronics projects I could possibly do and the most simple and cheap was an oscillator circuit I found here, which I modified, replacing a resistor with a potentiometer to control pitch (that version here). I bought all the parts I figured I would require and took a few hours to solder all of the pieces together according to the circuit. I plugged a guitar cable into the audio jack wired to the RC4558's 2nd OP amp's Output for the Tip and I grounded the Sleeve to test it. No sound would come out though. I checked all connections and it seems they're soldered tight, and I even did many continuity tests and voltage checks with my multimeter. I have no clue what I could have done wrong, as I am a beginner into electronics with little experience on building cool stuff. I made a video showing my build and how it's wired to the best extent I could, any questions on it I will answer. I appreciate any help that could be given, and I apologize if I had left out any important information.

 

sghioto

Joined Dec 31, 2017
1,038
Well for starters the board is kind of a mess but that's normal for beginners. However I believe your circuit will require a bi-polar supply as configured using the 4558 chip. Bi-polar just means it needs two 9 volt batteries.
I have redrawn your circuit to indicate the pin numbers and battery locations.
Basically, check and make sure the components are connected as in the schematic and double check the solder connections.
SG
EEE4558 triangle wave gen.PNG
 
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Thread Starter

skullkid2802

Joined Feb 1, 2019
6
Well for starters the board is kind of a mess but that's normal for beginners. However I believe your circuit will require a bi-polar supply as configured using the 4558 chip. Bi-polar just means it needs two 9 volt batteries.
I have redrawn your circuit to indicate the pin numbers and battery locations.
Basically, check and make sure the components are connected as in the schematic and double check the solder connections.
SG
View attachment 169226
Hi SG,

I seriously am so appreciative of this new circuit you have drawn, as it had solved the elusive mystery of why my circuit didn't work. I luckily was thinking ahead when I bought parts so I bought an extra battery and connector, making this fix a simple and easy solder. I will post a video of the working oscillator in the morning, currently it is 11:32 at night in my house, and I'd like to make the demo at full volume! I cannot believe it works, this is my first circuit ever, and it was a success thanks to you, the resources at falstad.com, and the All About Circuits platform for providing a place for people as clueless as me to find answers, learn and succeed at making electronic devices. Enjoy your evening.

Jack H.
 

wayneh

Joined Sep 9, 2010
16,162
An alternative is to not use ground as the reference voltage. Apply about half the supply voltage to those pins instead. A voltage divider (two identical resistors) between the poles would work. Use the voltage in the middle instead of ground.
 

sghioto

Joined Dec 31, 2017
1,038
it was a success thanks to you, the resources at falstad.com, and the All About Circuits platform for providing a place for people as clueless as me to find answers, learn and succeed at making electronic devices. Enjoy your evening.
Jack, you are welcome. Now that you have it working which is the first step the circuit can be configured to work on just one battery as wayneh mentioned above with the addition of a few more components.
SG
 

Thread Starter

skullkid2802

Joined Feb 1, 2019
6
An alternative is to not use ground as the reference voltage. Apply about half the supply voltage to those pins instead. A voltage divider (two identical resistors) between the poles would work. Use the voltage in the middle instead of ground.
Thank you both again for the help, I certainly would like to figure out how to only use one battery of course, how would I go about doing that schematically? Should there be 2 resistors added to each wire going to the power supply pins? Also, I powered the circuit this morning to test it, and something must have happened over night, as it no longer works :(. It's alright though, I'm sure I'll figure it out, maybe I do need to configure it for 1 battery. Once I get it running again, I surely will post a video. I appreciate all of the help.
 

AnalogKid

Joined Aug 1, 2013
8,254
I found online a version of your schematic reworked for a single voltage power source:



Note - pin 3 of the right-side opamp ("+4.5V") connects to the "reference node", the junction of the two 10K resistors.

To lower the reference node AC impedance (geek-speak), add a capacitor from the Reference node to GND. The cap should be fairly large, especially if you are using output frequencies below 1 kHz. 10 uF minimum, 100 uF is better. For better performance at higher frequencies, add a 0.1 uF ceramic cap in parallel.

What about those two resistors? There is a tradeoff - the larger they are, the longer the battery lasts. The smaller they are, the more stable the circuit is with changes in load current, operation at low frequencies, etc. I'd say 10K each as a max, and 1 K each as a min.

AHA - found a better image on the innergoogle.

ak
 
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MrChips

Joined Oct 2, 2009
19,923
Here is the circuit I used in my "pong" game. It is the same configuration as the circuits shown in posts #2 and #7.

Note that I have the pin numbers at pins 5 and 6 correctly labeled.

triangular wave generator.jpg
 

wayneh

Joined Sep 9, 2010
16,162
Thank you both again for the help, I certainly would like to figure out how to only use one battery of course, how would I go about doing that schematically? Should there be 2 resistors added to each wire going to the power supply pins? Also, I powered the circuit this morning to test it, and something must have happened over night, as it no longer works :(. It's alright though, I'm sure I'll figure it out, maybe I do need to configure it for 1 battery. Once I get it running again, I surely will post a video. I appreciate all of the help.
You can use just two resistors to establish your center bias reference voltage, and route that to both inputs. They don’t need to be established separately
 

sghioto

Joined Dec 31, 2017
1,038
Note that when using a single battery the 4558 output pin #7 will have a dc voltage of around 4.5 volts. In this case we will add coupling capacitor C1 to block the dc from going into the amp. Also added is level control R1. If you don't need it then replace R1 with a 10K resistor.
SG
EEE4558 triangle wave gen one battery.PNG
 

Thread Starter

skullkid2802

Joined Feb 1, 2019
6
Thank you everybody for the help. I unfortunately broke a pin off of the IC socket when trying to separate two blobs of solder that were creating a solder bridge between 3/4 of the pins on one side. I am not the best at circuit design, and soldering to a board so this may have been the reason it stopped working. I am going to order some more parts and create a new version of the circuit with the coupling capacitors, and once that's done, I will post an update if it works. I appreciate everyone for being able to bring this small project to life! Have a good day.

Jack H.
 

wayneh

Joined Sep 9, 2010
16,162
Thank you everybody for the help. I unfortunately broke a pin off of the IC socket when trying to separate two blobs of solder that were creating a solder bridge between 3/4 of the pins on one side. I am not the best at circuit design, and soldering to a board so this may have been the reason it stopped working. I am going to order some more parts and create a new version of the circuit with the coupling capacitors, and once that's done, I will post an update if it works. I appreciate everyone for being able to bring this small project to life! Have a good day.

Jack H.
You might consider getting yourself a breadboard for trying out circuit arrangements before committing them to PCB. I never go straight to soldering without experimenting first on my breadboard.
 

Audioguru

Joined Dec 20, 2007
11,251
Most circuits built on a solderless breadboard do not work due to the errors caused by the tangle of wires all over the place, the intermittent contacts and stray capacitance between all the rows of contacts and wires.
I built thousands of single or only a few circuits soldered on stripboard with the copper strips cut short with a drill bit and the strips and a few short jumper wires formed half of the wiring of a pcb, then the parts formed the other half. Some circuits were VERY complicated but worked perfectly. Only one wire was in each hole so a part change was easy using a solder sucker. The finished stripboards looked good enough to be the finished products that were sold.
 

wayneh

Joined Sep 9, 2010
16,162
Most circuits built on a solderless breadboard do not work ...
Oh c'mon, you know that's not true. There are thousands, maybe millions of folks using breadboards and perfectly happy with the results. I'm one of them. If you don't have the discipline to keep things neat on a breadboard, you're not going to get better results going straight to a PCB.

I agree breadboards aren't useful for high frequency (>100kHz or so) projects or high quality audio, but this project isn't either of those.
 
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