- PP4 -
I could not get the idea of an automatic feeder bank out of my head. It has a lot of advantages compared to a pin-driven feeder. The main goal was to make the design as simple as possible.
The best way to advance the tape is to wind up the cover tape only. This automatically advances the component tape. The problem is how to detect the position of the tape. An optical solution using a photodiode and infrared LED to detect the holes in the component tape is the easiest way but does not work for clear tapes. A mechanical detector solution will work for all kinds of tapes.
I had a look around to find a small detector switch and found one out of the Panasonic AV4 series that is perfectly suited for this tasks. Its size is only 7.5mm by 4.5mm by 2.5mm and the actuator size of the AV4404 is only 1mm by 0.8mm. The actuator is well rounded at the sides to easily detect the holes. To avoid a stuck actuator the switch is mounted at a slight angle. A spring driven plastic pressure plate (green on the section view below) presses the tape up against the switch but does not touch its actuator. This works for paper tapes as well as for thinner plastic tapes. The pressure plate also stabilizes the tape in vertical direction. This minimizes the risk of parts falling out of the tape wells.
The photos below do not meet the actual state of the feeders. E.g. I have removed the deflector shaft for the cover tape, changed the mounting angle of the windup motors and altered the cover plate. The actual building state can be found within the CAD drawings available in the download area.
A cover on top has slots in it to guide the tape in horizntal direction. Small holders on top hold each switch in place. One could also use small PCB's to hold the tape but I did not want to order a new PCB for now.
Modified modell servo motors are used as geared motors to wind up the cover tape and advance the component tape. The spools are turned out of POM. They can hold (calculated) 3m of cover tape each resulting in 375 x 8mm pich components. Then the cover tape has to be reassembled.
The current block has the following slots:
- 13 x 8mm tapes
- 3 x 12mm tapes
- 3 x 16mm tapes
- 1 x 24mm tape
A small controller PCB controls up to 20 feeder slots using a dsPIC 30F4011 and some IO extension. It uses RS232 over USB to communicate with the PC. The servo motors are PWM driven by a discrete P-N FET half bridge for each servo. Each servo can be stopped fast by switching the upper half of the bridge on. Holes in the feeder block will later be used to guide the cables to each microswitch.
The reels are held on a single shaft to avoid additional friction. They can be changed by putting them all onto two holder shafts using slotted holes for the centre shaft.
Note that on the following pictures of the feeder not all slots are fully assembled.
Here are some more photos of the complete unit. Some changes to the cover plate were necessary to prevent components from getting stuck when inserting a new component tape.
The second feeder is mounted on the right side of the machine and has a different slot width composition:
- 8 x 8mm tapes
- 4 x 12mm tapes
- 4 x 16mm tapes
- 2 x 24mm tape
On the pictures below two servos are missing. They are on backorder.