Another little project has come my way, it will involve a number of small projects that will come together eventually.
This is the first element, a fox with a waggy tail that appears and disappears as if by magic :)
Step 1: The Design
I found a nice laser cut MDF fox on Ebay. I wanted it to have some movement so decided to cut off the tail and make it wag... I also wanted to move the whole thing up and down so I worked out a circuit that will be operated eventually by a single pole changeover relay and a single power supply.
It would need 2 geared motors and 2 microswitches to make it work.
Step 2: Parts List
Aluminium offcuts in various thicknesses
Laser cut fox in MDF, unfinished
The remainder of the items were sourced from reichelt.com an online retailer for industrial and consumer electronics – they offer a range of tools, components, tech accessories and more – save up to 20% on many products.
geared motor 2 required
microswitch 2 required
rectifier diodes As many as it takes to fine tune speeds
terminal block 4 way (supplied as 12 way)
Various screws and nuts
Brass oddments for cams etc.
Odd pieces of plastic recycled from other things......
Step 3: The Build Begins
I started off with the tail wagger,
I found a lump of plastic with a hole in it that was a little smaller than the geared motor, I drilled it out to the correct size at an angle to keep the tail as close to the body as possible, the motor is held in place with a an M3 screw pushing against it.
There is a horizontal through hole that will be the pivot and another, in the side, tapped M3 to attach the connecting rod "J" link.
Step 4: Crank and J Link
This is all suck it and see stuff, I started by mounting the gear motor and tail wag block to a piece of aluminium sheet, measured the centre distance from motor to J link pivot point both up and down, that gave me the crank offset (20mm in this case). I turned up a hub to fit the motor and soldered it to a disc that will operate the microswitches and the crank. Once this was mounted I made a cardboard J link to get it the right shape to miss everything as it rotates. then it was remade in aluminium.
Step 5: Switches
I filed one indent for the switch operating rollers into the cam plate then arranged the 2 switches so that one would turn off the power fully up and the other when fully down, these were screwed to another flat piece of aluminium attached to the motor mount plate.
The last jobs were to cut a clearance slot in the switch plate and bend it at 90 degrees to enable later mounting.
Step 6: Wiring and Fine Tuning
The wiring took no time at all as it was pretty simple but when I powered the assembly for the first time I discovered that I needed to increase the voltage from 1.5 volts, that I had used to get the required speed of movement, to 3.5 volts to overcome the inertia of the swinging assembly.... this made the drop down too fast and the tail wag was a blur!
This is when rectifier diodes become very useful as they have the effect of dropping the voltage in a circuit by 0.7 volts each so 2 diodes in the tail wag and another 2 in the drop side of the circuit got the speeds back to where I wanted them.
It was around this time that I painted the fox with paint pens and permanent markers.