PicAxe Projects > PicAxe-08M Servo Controller V2

Finshed PicAxe08M Servo Controller V2

Finished Servo Controller V2

PicAxe 08M Servo Controller V2

PicAxe 08M Servo Controller V2.8 inspired by TrainElectronics


Final Notes and update: One last revision! The current version is 2.8, AND everything works! The PicAxe 08M can be programmed in circuit (I just put a jumper wire instead of a jumper connector). The LED power indicator and the switch to trigger the event all work as advertised. I am updating the section on adjusting because I am using larger potentiometers than the version 1 project. I also changed out the 33 ohm resistor for the LED with a 470 ohm resistor (that is R4 on the schematic). The LED was getting way too hot. I suspect that this is a function of the wallwart. So, your mileage may vary. See the section on adjusting...

NOTE: Now on version 2.8 of schematic! The schematic above is now correct. The updated files have been posted. Apparently, when I added the power section I disconnected teh ground circuit for the PicAxe 08M. Needless to say, it didn't work. I also did some minor re-arranging of the programming connector. Didn't affect the schematic, but it will physically work better.

Circuit used: The ciruit was largely taken from TrainElectronics.com. I drew it up in DipTrace (you can download the V2.8 Diptrace files here). The only difference between the version 1 and version 2 of this project is that version 2 is powered by a wall wart and two more standard potentiometers (I had to actually make the patterns for Diptrace).

Parts List: PicAxe-08M, 8-Pin DIP socket, 2 10K resistors, 1 22K resistor, 2 3-pin headers, and 1 2-pin header (may substitute a jumper wire instead), 2 100k potentiometers, and circuit board, a 7805 voltage regulator, a .1mf and 10mf capacitor, an LED and a 470 ohm resistor for the LED (R4). Also needed is a power jack and some sort of switch (can be a push button, magnetic, proximity, or something else). I also used some 3 pin header connectors from old mainboards (I cut the middle pin out for the 2 pin connection for the switch).

Construction Notes: If you look closely at the PCB layout, there are two jumper wires that isn't on the schematic, but it couldn't be avoided. I found a suitable pattern for my new potentiometers, not perfect, but close enough. I used my toner transfer method to make the PCB. I also added better markings for the silk screen (programming and servo headers).

It now has powe on board, so you can use any wall wart up to 12 volts. See the version 1 write up(PicAxe-08M Servo Controller V1) for the programming adapter.

Programming: You can get the programs from the TrainElectronics web site, or from here.

Adjusting: I put both pots at mid range (pointing straight up, away from the board). Inevitably, the servo will top out and hit the stop. Using the Range pot, start turning in counter clock wise a bit, then trigger an event. Eventually, it will do a full cycle with out topping out. Then start adjusting the Start pot to get the maximum range. From here you can adjust the starting point and the range to your hearts desire!

Toner Transfer Note: the bottom of the board is NOT mirrored before printing! It seems like I have messed this up more than once. Just flip the text. The silk mask gets mirrored AND the text flipped.

Toner Transfer, step 1
This is WRONG! See note at the begining of this page. The TT paper shifted a bit during the transfer. Not a big deal, just looks a bit off. It will still work. I may just trim the board abit after etching.
Copper Side
Properly (NOT!) etched copper side. Note the potentiometers are on the left as you look at the bottom of the board.
Silk Mask
Top side of the board. The markings are better, but it is wrong. See the begining of this page. I added markings for the programming cable and the servo connector. There is now on-board power and a power LED.
V2.5 Copper Side
Here is the new (NOT correct) copper side. I changed the copper pour so that you can tell it is different at a glance. I fixed the problem with the power adapter for the wallwart. Ended up adding another jumper.
V2.5 Silk Mask
Here is the new (NOT correct) silk mask for the parts side of the board. I had to move a few things around to make it work. Now there are 3 jumpers (including the programming jumper).
V2.7 Toner Transfer Complete

Here is the new (V 2.7) copper side. I changed the copper pour (again) so that you can tell it is different at a glance. I fixed the grounding and power issues.
V2.7 After Etching
Here is the new board (V 2.7) after has been etched. I am hoping that this will be the last etching of this board!
V2.7 Silk Mask
Here is the 2.7 version of the silk mask. I have high hopes for this one! If I have to re-do it again, I am going to have to make another parts run.
V2.8 Back of the Board
Here is the new (V 2.8) copper side. I changed the copper pour (again) so that you can tell it is different at a glance. I used some very old Tinnit to plate the copper. It definately helped the solder flow better.

V2.8 Under TestHere is the final V 2.8! I hope you enjoy making and using it as much as I did building it.


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