The Most Useless Machine EVER!

Step 6: Original Design Using 555 Timer

For ease of construction, I highly recommend going with a modified servo or a gearbox motor instead of using the 555 timer circuit show below.� There is almost nothing to be gained, or any improvement of operation of the machine using this circuit and a standard servo.

Some drawbacks in using the timer circuit are:� you have to use a 4 cell battery pack.� It won't run on any less voltage.� This will ensure that the servo will run very quickly, sometimes too fast in my opinion.� Using a modified servo, you can use 3 or possibly even only 2 cells, making the machine run at a slower, more spookier speed.�

Another drawback of using the 555 timer version is placement of the mechanical parts are limited due to a standard servo only having 180 degrees of rotation.� Using a modded servo or gearbox/motor will allow easier design and placement of the parts.

The only advantage with using a standard servo and the circuit is that just about any servo can be used, and if it should break or wear out, replacement is simple.

But when pondering the concept of the Useless Machine, perhaps going with the most complicated version is the aesthetically superior choice. � �


Note:� if you need more rotation from the servo, change R3 to 10K.

sirus20x6 edited the 2nd schematic putting the pins in order.
colin55 provided the 3rd version.

All of the schematics are basically the same circuit, just arranged differently.
�

Comments

[diesel08779]

in what scheme is the 555 timer being used? i'm a beginner in electronics but i can't figure out how to get this thing to work... i think maybe i have the wrong switch?

[Frivolous Engineering]

If you want to use a standard, unmodified servo then you need to use the 555 timer circuit to control the servo. Or you can do away with using the 555 timer circuit by modifying the servo, changing it to a simple gear motor. Using this method, only the switches and battery are needed. No control circuit is needed. Which ever way you go, the toggle switch is the same: a Dual Pole, Dual Throw (DPDT) switch.

[diesel08779]

hmmm... i think my problem lies within the switch, i think i have the wrong one. The switch has three positions, no two... didn't notice that before, i'll try that now. I just realized my question was a little vague, the timer that is being used, is what scheme is it being used? : monostable, astable, pulse width, pulse position... thats what i meant :)

[xxaznitexx]

I completed the circuit as shown in the diagram, and the motor turns a full 90 degrees. however, when it hits the switch, the motor doesn't do a full 90 degrees back. Instead it does about 45-60 degrees back. Can anyone figure out why? Is it the resistor value problem or some wiring problems...?

[Frivolous Engineering]

You're using the 555 timer?  If so, step 9 talks about aligning the arm.

Let me know if that helps!

[jimipop]

Hello saskview !

Thanks again for your advice ... now it perfectly works !

just another question, i'm a beginner in electronics, i want to "pimp" my box with a led so where could i connect it to make it light when it's on ???

a bientot!

[92033]

See my post I just made above...regardng use of a Electronic Flash Unit from a Disposable recycled 35 mm film camera...sounds like a fun project to build and use.

[Frivolous Engineering]

Connect the led to the switched power:  the pin on the toggle switch that is connected to pin 8 and 4 of the 555 chip.

[toben222]

Hi, I built a useless machine for myself, and i just wanted to add that i had huge difficulties with the circuit which is given here. You better use Potentiometers and a Oszillograph to adjust pulse length and distance (rather then just resistors). and you might add a condensator between x and -. 

When the servo turns, voltage shrinks, which will reduce the pulse length, which might make your servo turn back and forth like hell and might destroy it. so i just added another 6V power which just powers the servo, pulses are powered by their own 6V.

[akula169]

For some reason, the one I built is eating batteries. 

More research shows that I get about .1 volts when I read across ground and common on Switch2 when it is in the closed position.  I'd imagine this value should be zero.  Am I wrong?

Does anyone else this bleeding voltage issue?

[MrPhelps]

You should see the battery voltage across ground and S2 common. The circuit should not consume any power when in the closed position.  You must have something wired incorrectly.

[tydarby]

I have NO idea what to do with a 555.  I have zero experience with electronics let alone IC circuits.  But this little box has really perked up my interest in learning about it.  

Came across this the other day while searching for info.  Has a cool animation on the workings of the 555.  I still don't understand them but it's a start.  Click HERE.

[sungam3d]

I was looking at the design and circuit, seems a bit to complicated for new people to work with 555 timers, resistors and all that.

I have come up with the same circuit but simplified to just 2 switches, motor and battery.

Much easier I think.

http://img163.imageshack.us/img163/8618/uselessboxschematics.jpg

[TimsMule]

Thats how i built my useless device. Much easier to build than the other way in my opinion.

Heres some pictures  :

http://img694.imageshack.us/i/pc100029.jpg/ - finished device
http://img190.imageshack.us/i/pc100028a.jpg/ - push button used to break circuit
http://img709.imageshack.us/i/pc100027a.jpg/ - inside device
http://img94.imageshack.us/i/pc100026.jpg/ - electronic components

[willrandship]

Won't that eventually hurt the motor though? It will constantly ram the side and grind gears!

[TimsMule]

haha, im not sure. This is the first device ive actually built :)

There doesnt seem to be too much force imparted onto the gears, so im hoping it will all hold up nice.

[willrandship]

Does it still use a timer circuit? if it does then there's probably not too much to worry about. What I was worried about is like when you don't let your cd drive open and it burns out the motor.

[TimsMule]

Oh i see what you mean.

Well, when the lever comes down, it holds the push button down inside the box and breaks the circuit. So, the whole device is turned off without using a timer.

Gotta make sure the motor has a gearbox btw, otherwise it wont hold down the button while theres no power.

[willrandship]

Nice idea!

[txoof]

I started out with your circuit because it looked so much simpler, but unfortunately I didn't understand that a servo isn't a plain old motor.  

 Your circuit works great with a plain old motor, but won't work with a servo that hasn't been lobotomized.  The servos expect a pulsed input to drive them that the 555 timer supplies.  If you rip the guts out of a servo or just solder leads directly to the motor this method would probably work.  I don't know what the voltage rating is on a "standard" servo however so you might want to be careful if you were to do that.

Thanks for the great schematic though!  It certainly is easier to build than the version with the 555.

[willrandship]

What a waste of a servo! They cost like four times what a motor costs!

[txoof]

 The big advantage to using a servo is you get the gear box with it.  If you're more careful than I was, it is trivial to solder leads directly to the motor terminals and leave the rest of the circuit intact.  Then, should you want to use the servo for something else later, you just de-solder the leads and go on your way.

[doryrhp]

I'm not sure what a servo costs but I used the motor and gearbox available at the following site:

www.hobbyengineering.com/H1210.html

It is basically the mechanical bits of a servo without the electronics.

[willrandship]

Plain servos are actually pretty pricey...you can find them anywhere from $10 to $100, depending on power and build quality. However, that is probably because of all the PWM circuits for driving it. Those circuits are left out, hence the extreme price drop.

[legless]

And if you only need small 7.5g or 9g servos, you can pick them up on Ebay for $15-$20 for 6 including international shipping.

[mario59]

...definitely agree!!!
SURE is worth to use a simple wire-switch method instead of a 555 and other electronics components!
Compliments for the NEAT schematics!!!!
ciao
Mairo

[kingbling11]

 Hi, Where do the three wires for the servo connect on the second schematic?

Thanks
Zak

[daw123]

The servo connections are as follows:

The red cable from the servo conects to +ve terminal on the battery pack.
The brown (or black) cable from the servo connects to the ground (or -ve) on the battery pack.
The yellow (or orange or white) cable from the servo connects to pin 3 on the 555 timer. 

I hope this helps.

[Toy-soldier]

I recommend you not to connect the red cable from the servo directly to the battery pack. Make sure the switch is between them so the servo won't be powered when the machine is turned off.

[Frivolous Engineering]

Toy-soldier is right.  You want switched power for the servo.  Connect the red wire to pin 8 on the 555.

[daw123]

Sorry about the confusion kingbling11.

After SaskView and Toy-soldier's advice I changed the +ve connection on my machine.

[jeff.hillman]

I have built a prototype of this circuit with all of the listed components on a breadboard.  Everything seems to work correctly, but when the DPDT switch is in the position that puts the servo back to its starting position, the motion of the servo is kind of rough.  The motion is very smooth when the servo is moving "forward", but it almost looks like the connection is bad on the way "backward".  It does move all the way back to the starting position, but it pauses for tiny amounts of time during the trip, with between one and three pauses.  I have several of each component, including the servo, and swapping out each of the components one at a time to try to identify a bad part didn't help.  The servo also makes a very quiet buzzing noise during the backwards motion while it is moving and even after it has stopped, as long as there is power to the circuit.  The servo I am using is an Airtronics 94322.  Any ideas?

[colin55]

You need to build this SERVO TESTER project to find out exactly what mark-space period you need for the forward and reverse direction for your particular servo.   It is called SERVO CONTROLLER but you will be using it to determine the values you need for forward and reverse direction.
The details are from TALKING ELECTRONIC website. See 50 -  555 Projects in the left index.

[jeff.hillman]

I didn't go as far as building another circuit, but I did install a 100K pot in the place of R2 and found that the default position of the pot of 50K ohms resulted in a much smoother motion.  I don't know if the increased resistance is what helped or if all the 27K resisters I have are somehow bad.

[colin55]

Don't forget, the 100n has a 20% tolerance and the width of the pulses is very critical. Your servo needs 50k.

[colin55]

To get a .gif of the circuit diagram you will have to go to Talking Electronics website and see   50 - 555 Projects in the left index.

[colin55]

[Probasco]

 When did 7,6, and 2 become connected?  I am trying to figure that out...

[Frivolous Engineering]

Always were:  pin 2 is directly connected to pin 6.  The resistor and diode connect pin 7 to 6...

[anima6]

 Hi all
at first great THX to Sasview for this tutorial.

But,i have the same problem as xained described, it only turns in one direction, in my case the back direction.
I have the black wire from the servo on pin 1 and the red one on pin 3, is this correct? What about the white wire from the servo?
Any Suggestions?
(sorry for my bad english, je suis francophone)