Picaxe 18M with servos

[OldTinkerer]

I have been trying, whthout success, to get a Picaxe 18M high power to control servos. I also tried the non-high power 18M nd that also would not control a servos. Strangely I also tried an 08M2 and that controlled the servo without any problems.
I am now considering modifying one of the I/O ports (e.g B0) on the 18M high power, but would need advice.

Has anybody else successfully managed to get ab 18M high power to operate a servo?

 

[AllyCat]

Hi,

By high power (board?) do you mean a PCB with an extra "driver" chip? Those chips are usually "Open Collector" (and inverting) so you probably need to remove the chip and put a link (or links) between its relevant input and output pins. If that seems to be the problem we can probably help if given a few more details of the PCB and/or Chip numbers.

Cheers, Alan.

 

[hex]

I agree 100% with AllyCat.

If you are using board CHI035 then there is no easy access to PICAXE output pins.

If you are using board CHI035A, then there is an option to fit 2.54 header pins directly to PICAXE output pins. Choose an output pin for servo control and wire 0 Volts and +5V to 3-pin servo.

Maybe you are using some other "18M high power" board. More information needed

non-high power board sounds more promising, but please tell us exactly which board(s) you have

 

[OldTinkerer]

The board is a CHI035A and and the problem seems to arise when trying to drive servos in parallel with the FETs and bi-directional driver chip.

BUT I have just done my own ,'bodge trial' where just using a 220 ohm resistors directly into port B.0 but coming out directly rather than going through the FET then seemed to work with the simple servo comands. So I think all I now need to do is to remove and replace the FET with the resistor.

But thankyou for your time and patience.

 

[AllyCat]

Hi,

The board is a CHI035A and and the problem seems to arise when trying to drive servos in parallel with the FETs and bi-directional driver chip.

The link to the datasheet in the PICaxe Store appears to be broken, but it is HERE. I don't know the exact details of the board but the FETs are inverters and might "fight" any resistor bypassing them. Better to remove the FET(s) [EDIT: Ah, I see you said that] and/or disconnect the connection/track to any (one) of their terminal(s) , i.e. Gate, Source or Drain. Or if you're not using IC2, remove it and link pads 10-11 , 14-15 , 2-3 ,and 6-7 as required, for B.7 , B.6 , B.5 and B.4 .

Cheers, Alan.