re increasing servo output angle

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re increasing servo output angle

Post by chlluk » 15 Mar 2018, 07:18

I'm working on a replica Bellamatic servo for my new Grundig system. I am following Shaun's idea of fitting a modern servo in side the body. Normal servo output angle is in the order of 60 deg, I need to double that to 120 if possible, Its the small reduction gear train in the bellamatic.
Can I rework the feedback pot with resistors in some way to increase the output angle or is there a commercial servo out there with a wide angle output.

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Re: re increasing servo output angle

Post by Phil_G » 02 Dec 2018, 17:22

Hi Clive, sorry I only just noticed this post.
If its still a problem, some years ago I used to make servo-stretchers for the FPV camera lads, ... e-easy-way
Its 1uS resolution, replaces any out-of-spec pulses with last-known-good and does a bit of filtering for smoothness. Its in pic assembler for the 12F675 which I believe you can do? Here's the hex file.
If not I can do just the chip or a ready-made stretcher.

Code: Select all

heres the header for info
; STRETCH.ASM - Servo pulse doubler makes 1-2ms pulse into .5 - 2.5ms pulse
; Pulses outside the 1-2ms range are assumed to be glitches and are replaced with last good pulse value.
; Fuses - WDT enabled, code protect, Power on reset enabled, 4Mhz intRC osc
; Channel input on GPIO3 and output on GPIO4.
; Phil_G, Jan 18th 2008

Attached is a doc with some important notes:
(28.5 KiB) Downloaded 35 times

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Re: re increasing servo output angle

Post by tiptipflyer » 14 Dec 2018, 11:33

Hi Phil,
this morning, I tried out, if I am able to get one of these things working. It was no problem at all. Programming the PIC12F675 was very easy and the Servo Doubler works great.

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