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Mechanics and Construction => Mechanics and Construction => Topic started by: offy on March 04, 2009, 07:14:55 PM

Title: Modify servo with replacing P.O.T
Post by: offy on March 04, 2009, 07:14:55 PM: I want to replace the P.O.T. Could I use a 1.62K OHM 1/4W 1% Metal Film in airman00 tutorial on how to modify a servo?

http://www.societyofrobots.com/member_tutorials/node/82 (http://www.societyofrobots.com/member_tutorials/node/82)
Title: Re: Modify servo with replacing P.O.T
Post by: Ro-Bot-X on March 04, 2009, 07:20:43 PM: I have used 2 resistors, both 2.7k, in series, with the middle connection tied to the board where the middle of the pot was, just like in Airman's tutorial.
Title: Re: Modify servo with replacing P.O.T
Post by: offy on March 04, 2009, 07:23:29 PM: Can I use a 1.62K
Title: Re: Modify servo with replacing P.O.T
Post by: Trumpkin on March 04, 2009, 07:25:41 PM: Probably not.
Title: Re: Modify servo with replacing P.O.T
Post by: offy on March 04, 2009, 07:28:21 PM: So the resistors go to the 5v and ground, than they connect and go down the middle one (pulse)
Title: Re: Modify servo with replacing P.O.T
Post by: Trumpkin on March 04, 2009, 07:35:27 PM: Yep, connect one resistor to the left wire and the other to the right wire and then where they meet up connect it to the middle wire. Just like it shows in the tutorial.
Title: Re: Modify servo with replacing P.O.T
Post by: offy on March 04, 2009, 07:39:37 PM: The tutorial image was kinda confusing. But does anyone know if I could use a 1.62k. I don't think it will matter. But I am new to this so...
Title: Re: Modify servo with replacing P.O.T
Post by: airman00 on March 04, 2009, 08:21:22 PM: Quote from: offy on March 04, 2009, 07:23:29 PM
Can I use a 1.62K

Quote
* Two 2.2k resistors (actually, anything between 2.2k and 3.3k will work, as long as they are equal values)
Title: Re: Modify servo with replacing P.O.T
Post by: offy on March 04, 2009, 08:45:35 PM: Oh, I think I need to buy some new resistors than. I really don't know, I soldered the 3 wires to the pot since they came off and it doesn't work, it seems like they are not connected...
Title: Re: Modify servo with replacing P.O.T
Post by: Soeren on March 05, 2009, 01:28:48 AM: Hi,

Those resistors are nothing but a potential divider, so the only consequence in using 1k62 is a slightly larger current draw.
In other words, use whatever you have that don't suck up too much current. I'm not sure how high you could go, as I don't know the impedance of the input that sees the Vcc/2, (since I don't mess around using servos as motors), but I wouldn't be surprised to find a semi-high impedance (still, it probably cannot be too high, or it might be prone to picking up radio noise when used for R/C), but 10k resistors will very likely work.

Resistors/Current drain:
1k0/2.50mA
1k62/1.54mA
2k2/1.25 mA
3k3/0.75mA
Title: Re: Modify servo with replacing P.O.T
Post by: offy on March 05, 2009, 02:09:18 PM: Everyone says something different. I don't know if I should use the 1.62K or not.
Title: Re: Modify servo with replacing P.O.T
Post by: Trumpkin on March 05, 2009, 06:37:25 PM: Resistors are not expensive, so I suggest you just go by 2.7k ones, just to be on the safe side.
Title: Re: Modify servo with replacing P.O.T
Post by: offy on March 05, 2009, 07:28:13 PM: I used the 1.62k ones and it works fine. Thanks for all the help. If anything goes wrong I will be sure to buy 2.7k ones =]