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TabRobot Capacitor — Parallax Forums

TabRobot Capacitor

Jonathan AllisonJonathan Allison Posts: 96
edited 2005-01-16 01:54 in Robotics
Hello hello,

I posted earlier a post stating I could not get my tab robot to connect to my pc, loopback:no and echo:no. Its a serial cable, not a null modem and I have gone through many of the posts related to this. Now here is the catch. A while ago I broke off a capacitor (I think its a capacitor anyway). I soldered the capacitor back on, now the robot itself will work, IE spill the wheels etc, but I still have no connection.

Attached is a picture of the robot and a big black arrow pointing to the capacitor which I had to solder back on. Does anyone know what it does and what problems it might cause if its not connected properly? Like if it would cause the robot to not work at all then i know that is not my connection problem, but if it is primarily used for PC interfacing, then perhaps thats whats wrong, as it could be on backwards, if there is such a thing.

Argg, posted this in the wrong forum, sorry. Should have been in Basic stamp.
Thanks for the help.



Post Edited (Jonathan Allison) : 12/30/2004 12:31:18 AM GMT
2048 x 1536 - 349K

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2004-12-30 03:25
    Loopback should pass if you merely have a good serial cable to the SumoBot. There is a piece of wire on the Sumobot that connects RTS to CTS. This is the first check the Parallax IDE makes when trying to connect. If that is not working, then you don't have a good cable, or a good cable connection to the 'Bot.

    A 'null-modem' cable IS a 'serial-cable'. There are two flavors / pinouts of serial cables. One which has the wires 'straight-through' -- 1 to 1, 2 to 2, etc. The other DB-9 serial cable type is a 'Null-Modem' cable. It runs 1 to 1, 2 to 3, 3 to 2, 4 to 5, 5 to 4, etc.

    Loopback should pass, even if you HAVE a null-modem cable, though. It sounds like you don't have the Sumobot connected to the 'right' serial port, or you are using a USB adapter that does not properly connect the signals.
  • Jonathan AllisonJonathan Allison Posts: 96
    edited 2004-12-30 13:36
    Thanks

    I guess I should test the cable, like I said I tried a couple of PC's, same thing, no lookback, nothing. The cable is a new out of the package "Serial Extension". I have an ohm meter, I'll use that to test the cable, just to make sure. Although I am very doubtful that is the problem? Maybe I should hook the cable up to the breadboard instead of relying on the setup Tab electronics have?

    I know I seen a diagram around here somewhere that explains how to do that....



    Johnny
  • ForrestForrest Posts: 1,341
    edited 2005-01-16 01:54
    I just picked-up a Tab Sumo-Bot today at CompUSA for $29 - great price. I studied your picture and found out why your BS2 wasn't working. The yellow device you broke off and resoldered is NOT a capacitor - it's a 20 MHz resonator. Crystals and resonators are fragile - my guess is yours is broken. The BS2 won't work at all with a broken resonator. The part on my board is marked ZTA 20.0 MX and it looks like Digikey sells this part for $.49 - Digikey P/N X918-ND
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