Print PDF
Favorite
Email
Step 2How it works.
How it works
When the circuit is powered up, the C1 capacitor will initially be in a discharged state. Thus, the Trigger (pin 2) will be LOW, driving the Output (pin 3) to go HIGH. Discharge (pin 7) goes HIGH and goes ground. The cycle begins.
The HIGH Output will cause C1 capacitor to be charged through the R1 and D1 path. Upon C1 voltage reaching 2/3 of +V, the Threshold (pin 6) will be activated and drive the Output (pin 3) LOW. Discharge (pin 7) goes LOW. The time it takes for C1 to charge depends on the position of R1.
Since Output (pin 3) is now LOW, capacitor C1 will start to discharge through the D2 and R1 path. When the voltage of C1 drops below 1/3 of +V, Trigger (pin 2) will be LOW, driving Output (pin 3) to go HIGH, and Discharge (pin 7) to go HIGH and shorts to ground. The cycle repeats itself.
You've probably noticed by now that the circuit is using Discharge (pin 7) to drive the motor, simply by going ground in each cycle. You can add some amount of protection if you're concerned about back EMF from the motor.
Pin 4 and 5 are not used, and pin 1 is simply tied to ground. The circuit can take between +3v to +18v. The Frequency is around 144Hz. Do note that, doubling the value of C1 will reduce frequency to half, tripling will will reduce frequency to 1/3, and so on.
When the circuit is powered up, the C1 capacitor will initially be in a discharged state. Thus, the Trigger (pin 2) will be LOW, driving the Output (pin 3) to go HIGH. Discharge (pin 7) goes HIGH and goes ground. The cycle begins.
The HIGH Output will cause C1 capacitor to be charged through the R1 and D1 path. Upon C1 voltage reaching 2/3 of +V, the Threshold (pin 6) will be activated and drive the Output (pin 3) LOW. Discharge (pin 7) goes LOW. The time it takes for C1 to charge depends on the position of R1.
Since Output (pin 3) is now LOW, capacitor C1 will start to discharge through the D2 and R1 path. When the voltage of C1 drops below 1/3 of +V, Trigger (pin 2) will be LOW, driving Output (pin 3) to go HIGH, and Discharge (pin 7) to go HIGH and shorts to ground. The cycle repeats itself.
You've probably noticed by now that the circuit is using Discharge (pin 7) to drive the motor, simply by going ground in each cycle. You can add some amount of protection if you're concerned about back EMF from the motor.
Pin 4 and 5 are not used, and pin 1 is simply tied to ground. The circuit can take between +3v to +18v. The Frequency is around 144Hz. Do note that, doubling the value of C1 will reduce frequency to half, tripling will will reduce frequency to 1/3, and so on.
| « Previous Step | Download PDFView All Steps | Next Step » |
He wants to take an old video camera and hack the motor that drives the playback/record, adding a pot so he can change the speed.
I think this looks like it could do that. I assume I will probably need to add some kind of switch to turn it off/bypass it for normal speeds. And something to keep anything from getting fried.
The only real thing I would be concerned about is burning out the motor. It's not like it would be something I could just easily replace. Ya know?
Anyone have any suggestions/recommendations in regards to this particular use?