Hello, i have recently made a circuit on a PCB of a 555 timer in astable mode with a pot to adjust the oscillations. A 9v battery supply and an NPN transistor with flyback diode protection and a cheap 6v motor that comes in your average Arduino starter pack. I will have pictures below, I do not have one full schematic but pretty much the output pin of the 555 timer is feeding into the base of the transistor and controls the motor.
My circuit does work but i am not able to get the full range speed of the motor. It goes from Medium fast to very fast. Is this just about adding a larger OHM potentiometer?
And also with no motor hooked up i can get the led to blink (slow to fast) but when i hook up the motor it goes from blinking pretty fast to a solid color or high duty cycle.
Can anyone explain this?
Also, how high of a voltage motor can i scale this circuit up, if i supply more voltage?
What does that give you for an output frequency? What’s your duty cycle range?
What’s a reasonable PWM frequency for a small motor? Don’t know? What does an Arduino use for its standard PWM frequency?
Time to start thinking about what you’re trying to achieve. Oh, and what Steve said. You cannot achive 100% duty cycle with one 555. What does that mean to your desired behavior?
One last thing: you should have a bypass cap on pin 5. Not that it will change your results but just be aware.
Sigh... does no one know how to turn their phone any more?
When drawing a schematic, it is better to draw them by function. Otherwise, it is just a hand drawn pictorial.
I'm having a hard time parsing that. Do you have a 10k pot connected so when in the lowest resistance, it connects directly from 9V to pin 2? And Discharge is only connected to 9V. I have no idea how this is even oscillating, except that the motor is probably pulling the 9V line down, especially if this is a standard 9V transistor radio battery. No, wait, pins 8(V) and 4 (/reset) are connected together, but to nothing else. Is there a reason you've wired it up in this odd fashion?
If you really want to do this with one 555 timer, you can get from about 5% to 95% PWM duty cycle if you do things correctly.
Steering diodes can be used to alter both On and Off times. Note how much simpler this schematic is to understand:
Which schematic is easier to understand?
But you'll need a better power source than a 9V battery.
Keep in mind that the transistor requires the base current be about 1/10th the stall current of the motor.
thank you guys for response. I will take what you said into consideration.
I got the 555 timer circuit from http://www.circuitbasics.com/555-timer-basics-astable-mode/
can i generally trust sites like this to build schematics. And which transistor would you recommend for these speeds?
Thanks again
polymorph:
Sigh... does no one know how to turn their phone any more?
When drawing a schematic, it is better to draw them by function. Otherwise, it is just a hand drawn pictorial.
I'm having a hard time parsing that. Do you have a 10k pot connected so when in the lowest resistance, it connects directly from 9V to pin 2? And Discharge is only connected to 9V. I have no idea how this is even oscillating, except that the motor is probably pulling the 9V line down, especially if this is a standard 9V transistor radio battery. No, wait, pins 8(V) and 4 (/reset) are connected together, but to nothing else. Is there a reason you've wired it up in this odd fashion?
If you really want to do this with one 555 timer, you can get from about 5% to 95% PWM duty cycle if you do things correctly.
Steering diodes can be used to alter both On and Off times. Note how much simpler this schematic is to understand:
Thank you for the response. you mentioned before that i can reach 100% with more than one timer, How does that work?
And thank you for the circuit you showed me. can you explain how this functions?
Thanks again
Which schematic is easier to understand?
But you'll need a better power source than a 9V battery.
Keep in mind that the transistor requires the base current be about 1/10th the stall current of the motor.
Thanks for the response. Could you explain how the circuit works that you showed me? Maybe i will try and make that one next. Thanks again
thank you guys for response. I will take what you said into consideration.
I got the 555 timer circuit from 555 Timer Basics - Astable Mode
can i generally trust sites like this to build schematics. And which transistor would you recommend for these speeds?
Thanks again
That reference makes no mention of a PWM circuit. They are all valid astable circuits.
You have missed placed some wires.
You basically are varying the frequency NOT the PWM with your "circuit".
Tom....
TomGeorge:
That reference makes no mention of a PWM circuit. They are all valid astable circuits.
You have missed placed some wires.
You basically are varying the frequency NOT the PWM with your "circuit".
Tom....
Thanks for the. I know now that I am wrong but i thought that an astable 555 circuit was PWM? can u explain the difference between varying frequency and varying PWM, and did i misplaced wires in the scematic?
Thanks for the video. It did clarify, but from what i understood from the video, When you are using PWM , you are splitting cycles of the signals into time segments and the amount of time its on determines the duty cycle. So would i be right to say the you can use PWM at different frequencies?
Hi,
Yes, usually you run at constant frequency and adjust the duty cycle.
Keeping the duty cycle constant and adjusting the frequency has little to no use in speed control.
