# Controlling simple servo motor forward/reverse pattern using 555 IC timer and H-bridge (no micro-controller) [on hold]

Need some help understanding how to build this circuit:

The user will switch the device on

servo motor rotates a gear for a constant number of revolutions in the forward direction

the motor then stops, waits 1/4 of a second

servo motor rotates a gear for several revolutions in the reverses direction for the same number of revolutions as in step 2

servo motor stops, waits 1/4 of a second

repeat steps 2-5 as long as the device is on

if the device is turned off, wait for steps 4 and 5 to be complete, then turn off completely.

The device is simply a small motor that connects to a gear set to increase torque, the rotation of the gears inverts a rack of test tubes up and down as long as the device is turned on. Will be battery powered so I would like to avoid using a micro controller.

From my research, I was thinking of using an H bridge to control the direction of motor. Now to control the H bridge, which is simply a set of transistors, I was going to use three 555 IC timing circuits. The first 555 IC will dictate the frequency of the forward motion H bridge activation, the second 555 IC will perform the 1/4 second delay for the third ICC timer, which controls the frequency of the reverse motion H bridge activation.

I have no idea how to perform step #7

Will my preliminary setup at least be able to perform steps 1-6?

Edit: The provided circuit is my preliminary drawing for using an astable multivibrator circuit linked to a 555 timer circuit. The two outputs of the astable multivibrator control two transistors that act as switches for the 555 timers two pwm channels. Two alternating pwm signals, one for forward, and one for reverse are sent to the servo from the 555 timer. Once the servo has turned completely 180 degrees, it will maintain that position as long as the pwn signal is provided for that direction. Timimg can be easily controlled by selecting the correct resistors and capacitors in the multivibrator.

## put on hold as too broad by Chris Stratton, Edgar Brown, Finbarr, awjlogan, Elliot Alderson2 days ago

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• "Will be battery powered so I would like to avoid using a micro controller" - doesn't make any sense. Come up with a better reason, or use a micro. – brhans Feb 10 at 2:53
• space is also extremely limited on the device. Will eventually be making into a custom PCB – Vincent D. Feb 10 at 2:58
• This is not remotely reasonable without a programmable element like a microcontroller, an approach that will save both power and space over the absurdly unweildy alternatives even in the unlikely case you could actually make them work. – Chris Stratton Feb 10 at 3:03
• Doing this with a microcontroller will be a lot friendlier to your batteries than not. 555s are not known for being low-power devices. – Hearth Feb 10 at 3:05
• I was looking at doing something like this: electronics.stackexchange.com/questions/6631/… – Vincent D. Feb 10 at 3:11