RC India

RC Models => Self-designed, DIY and College Projects => Topic started by: Swapnil on May 19, 2011, 06:46:06 PM



Title: Cheap Servo/ ESC Driver
Post by: Swapnil on May 19, 2011, 06:46:06 PM
Here's an inexpensive servo/ ESC driver I made (when I used to long for  a radio). It's based on a design given by Werner Soekoe in the Seattle Robotics Society newsletter. The circuit uses two multivibrators (IC 556) for generating a precise and stable frequency servo signal. The left part of IC 556 is used to generate a stable (but adjustable) frequency. The right part is used to control the pulse width (by means of 10k pot). The servo/ ESC plug is connected at CN2 (the + wire can be removed while connecting an ESC). The visual analyzer graphs (attached) show noise frequencies. These can be easily removed using a low pass filter. The circuit works really well if built properly.

Notes:
1) Points J1 and J2 are connected by jumper wires.
2) Connect capacitors as close as possible to IC pins.
3) Use a good quality linear 10k pot to avoid jitters.   


Title: Re: Cheap Servo/ ESC Driver
Post by: ujjwaana on May 19, 2011, 07:32:54 PM
Nice build swapnil! this is real neat. Adding a separate button for 'Servo Centering' would be an added advantage many of use these testers to do centering during our builds.
Which PC based CRO/DSO you used ? I have been eying on them but most of Sub $200 have low range of 4MHz and below.

I made a similar DIY tester a while back:
http://www.rcindia.org/self-designed-diy-and-college-projects/build-thread-diy-pic-based-servo-tester/
Not using it any more though  :headscratch:


Title: Re: Cheap Servo/ ESC Driver
Post by: ajith on May 19, 2011, 07:43:01 PM
good work  swapnil   {:)}

do  You have  any plans (circuits )  for  a Brushed  ESC   for  a 300 sized  motor !!

To be clear  the  motor  same  as in the    http://www.rcindia.org/for-sale/brushed-esc-with-reverse-function/msg49837/#msg49837 (http://www.rcindia.org/for-sale/brushed-esc-with-reverse-function/msg49837/#msg49837)     :salute: :salute:
 


Title: Re: Cheap Servo/ ESC Driver
Post by: warriornair on May 19, 2011, 08:11:11 PM
@swapnil, good work, do u have practise with SMD ,  it will reduce the size ... thanks for the post...........

@ ajith
 i think there is a post by ujwaana about that...... search for that


Title: Re: Cheap Servo/ ESC Driver
Post by: Sumeet on May 19, 2011, 08:12:07 PM
Are we supposed to join both J1 and both J2(ie; All four points) together. Or one J1 to another J1 and vice versa...?


Title: Re: Cheap Servo/ ESC Driver
Post by: Sumeet on May 19, 2011, 08:17:13 PM
Oh I figured how to join them...

Why would you name those 4 points with two different names if you are going to join them together. Right?

I think J1 goes with J1 and J2 goes with J2.


Please correct if wrong.....


Title: Re: Cheap Servo/ ESC Driver
Post by: Swapnil on May 19, 2011, 09:30:28 PM
Yes, J1 goes with J1 and J2 with J2.

@Ujjwaana:
The PC based CRO is 'Visual Analyzer' and it's free!


Title: Re: Cheap Servo/ ESC Driver
Post by: Samanth on May 19, 2011, 10:53:55 PM
Swapnil,
Nice job ! :thumbsup: the basic idea is to get a PWM signal output to manipulate the servos. The schematic seems to be simple.
how did you make that PCB ?
I normally use a copper clad pcb, and use the toner transfer method.

I've recently started using photosensitized boards.

I am planning to make a multicopter controller using Atmega48. I would like to know how you made your PCB :) ??


Title: Re: Cheap Servo/ ESC Driver
Post by: Swapnil on May 20, 2011, 05:12:35 AM
Thanks everyone! ;D

The circuit happened when I messed up with my E-sky ET6I. I made loads of servo drivers (some 555 based, some microcontroller based) but this one seems to be the best.

@Samanth:
I normally use a copper clad PCB and toner transfer too (and pretty efficiently ;)). However this one was made using vinyl tracks. I rely on vinyl tracks for small, straightforward circuits as they take much less time as compared to toner transfer and give better results with home-made super-etchants (This one completed in about 5-10 mins.).


Title: Re: Cheap Servo/ ESC Driver
Post by: Samanth on May 20, 2011, 07:40:08 AM
Oh..I thought so :)

you hand't posted pics of the track so I didn't know. Do you get vinyl tracks and super etchants in your local electronics store ? 



Title: Re: Cheap Servo/ ESC Driver
Post by: Swapnil on May 20, 2011, 07:55:02 AM
The vinyl tracks can be custom-designed (for simple circuits even the whole PCB layout can be designed) using softwares like 'SignGo Lite'. The tracks (or layout) can then be obtained using vinyl cutters. I get it done from a 'bike-stickers' shop nearby.
And the 'super-etchant' is home-made (using HCl and Hydrogen Peroxide). It is explained in detail here:
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

I also use this method:
http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/


Title: Re: Cheap Servo/ ESC Driver
Post by: Samanth on May 20, 2011, 08:16:53 AM
Thats some good information :)
thank you !