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Unique servo idea. Any help?

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bubsta82

New Member
I need help designing a circuit to control a standard servo to flip up and down a license plate. Before scolding me with how illegal this is i know! Mounted behind my license plate are 24 Infared leds and a micro camera which works amazingly at night! I am trying to keep my bumper as clean as possible. My problem is how to operate the 6v(max) servo to spin a desired distance and stop without using a servo controller. I am not doing this because i thought it was easier not to and cheaper. My idea was to mount two push button or tactile switches that would be pressed when the plate was in the up position and down position to turn the servo off. having a momentary toggle switch to flip it up and down in my cab. As well as knowing which switch is being held in by an led indication. Example, when the plate is in the up position a green light would be on and a red led would be indicated when it is down as a warning light. I would be able to just flip a switch up to flip up the plate and the same switch down to flip down the plate.

Any ideas welcome!
 

HarveyH42

Banned
I built a servo tester with a 555 timer, years ago. Got the circuit off the web, should be an easy find with Google, also posted on here several times. I'm using microcontrollers for such things now, that was one of my last 555 projects. Anyway, it uses a pot to move the servo arm, so you just need to determine the value of two resistors to replace the pot, and the toggle switch to choose between them. An LM7805 should be fine to drop the 12v down, but will need a heatsink.

Personally, I would mess with the tag, law enforcement around here are a little particular about them. They pull you over if its bent, muddy, not mounted in the correct place, or pretty much anything. It's very tough to spot them anymore, they'll drive any model car, some marked, some not, the light bars are all low profile LEDs anymore. You get caught, you will most likely go to jail, or be detain quite a while, until the decide what to do. Most cop cars have dash cams these days, to limit liability. IRLEDS stand out very well. Should probably think about this a little more, decide if it's really worth it. They don't like altered tags, specially when it's intentional, since the assume you have some crime in mind.

Don't know how big your camera is, but I have some that are pretty small, and a tiny hole through a taillight would only be needed. Shouldn't be noticeable, and a dozen or so IRLEDs could be placed anywhere, also with little work, or alteration of appearance.
 

bubsta82

New Member
I also came across this schematic which appears to operate on momentary push buttons.

**broken link removed**

now the two resistors before the switches should be variable to control the throw of the servo correct?
 

HarveyH42

Banned
I also came across this schematic which appears to operate on momentary push buttons.

**broken link removed**

now the two resistors before the switches should be variable to control the throw of the servo correct?

It pretty much as I described, push buttons, instead of the toggle you wanted. The value of the resistors determine which direction the servo goes, probably to the limit in each direction. For you, it's probably close, and once you find the right values, it would make much sense to leave it adjustable. The servo signal is pulse-width modulation. A 1 mS pulse will give you full swing in one direction, 1.5 mS is the center position. This should give you the 90 degrees of movement to flip the tag up, or you can go 180 degrees, and anywhere between.
 

Boncuk

New Member
I also came across this schematic which appears to operate on momentary push buttons.

**broken link removed**

now the two resistors before the switches should be variable to control the throw of the servo correct?

Be aware that there is no valid output if neither button is depressed. The timer circuit simply quits working.

The resistor values given in the schematic are pretty rough. Pulse lengths are <1ms and >2ms (1.5ms is the center position, which is omitted in the schematic.)

Boncuk
 
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