something specific. If not I'd assume that it was where the oPWM object
was, which was like 20KHz, WAY too high for the 754410 motor
controller. Check out the oPWMH specs and see what it takes to move
that down to 1 or 2KHz and see if that changes things.
DLC
Shaggy wrote:
>Off the top of my head, I don't know. However, I would expect that would not
>be an issue since the LCHB is sold by RogueRobotics to go with their OOPic
>board. I would not expect them to be including the LCHB if it won't work
>with the board they are using. I believe it was working as expected when I
>had it attached to the ATS motors, which are smaller than the Robotics
>Connection motors I am currently using.
>
>I'm leaning towards too much power draw. I'll try to look at that this
>evening. The motors can certainly draw too much power for the LCHB, so it is
>looking like I will have to replace that, regardless of whether that is my
>specific problem. After all, the 754410 is getting a bit warm, even with a
>heat sink, when I run the motors for 10s.
>
>Therefore, if anybody has a recommendation, I'll take a look at it.
>Otherwise I might just go with the H-Bridge sold by the same company that
>sold me the chassis and motors. I'm pretty sure that one will take enough
>power, though I will still have to look it over some.
>
>
>ooPIC Tech Support wrote:
>
>
>>What is the frequency of your PWM? The 754410 is happiest at 2KHz or
>>lower. At 20KHz I've detonated these chips!
>>
>>DLC
>>
>>ooPIC Tech Support
>>
>>-----Original Message-----
>>
>>From: Shaggy <charrington@idfg.idaho.gov>
>>Subj: Re: [oopic] H-Bridge issue...maybe.
>>Date: Sun Nov 25, 2007 12:38 pm
>>Size: 4K
>>To: oopic@yahoogroups.com
>>
>>
>>That's good to hear. Just having something hooked up wrong is a much
>>better
>>problem than faulty hardware. Now how to go about figuring out what it is.
>>
>>I have gone back to the manual for the Rogue Robotics ATS, and confirmed
>>that my code is exactly the code they have: IOLineP is 17 for one, and 18
>>for the other. IOLine1 is 26 and 24 respectively, and IOLine2 is 27 and 25
>>respectively. There really isn't any more code other than that for setting
>>up the oDCMotor2. To run the motors, there is a countdown timer which is
>>set
>>to a value in seconds. As long as it is greater than 0, the operate
>>property
>>for each motor is set to true. When the countdown reaches 0, the operate
>>property for each motor is set to false. That's the extent of the code,
>>though it is not all in one place.
>>
>>As far as hooking things up, I've also reviewed that. There is a ribbon
>>cable running from the OOPic to the Low-Cost H-Bridge (LCHB). This ribbon
>>cable is designed so that there is only one way it can be plugged in on
>>each
>>end, and the ends are plugged in as required. If the cable is
>>wrong....well,
>>I haven't looked at that.
>>
>>There are two pads for external power, which are labeled + and -. I
>>soldered
>>the red lead from the battery to + and the black to -. Simple enough. The
>>documentation then states that if external power is supplied, the jumper
>>should be moved closer to a named capacitor. I have confirmed that that is
>>set correctly.
>>
>>The only other connection I have made is between the motors and the LCHB.
>>The documentation mentions color coded wires, which I can't actually do,
>>since these motors have different colors, but I followed the intention
>>after
>>figuring out what the colors actually meant on the ATS motors.
>>
>>If this is a ground issue, where does it lie? The LCHB is designed to be
>>hooked up a certain way, and it is. If the connections that are actually
>>needed are not the ones in the documentation, it's going to be a pain to
>>figure out what's wrong.
>>
>>A couple things I'd have to look at are these:
>>
>>1) Do the connections on the ribbon cable actually lead to where they
>>should
>>lead? I think I don't necessarily need to test this, because it was
>>working
>>(I think) with the ATS. I'm pretty sure I tried it with lower speeds,
>>though
>>I was not using external power.
>>
>>2) What does the jumper actually do? The documentation states where the
>>jumper should be, without explaining anything about what it does. Should
>>be
>>simple enough to trace, though not so easy to get to the board anymore.
>>
>>Is there anything else I should be checking out?
>>
>>
>>
>>rtstofer wrote:
>>
>>
>>>--- In oopic@yahoogroups.com, Shaggy <charrington@...> wrote:
>>>
>>>
>>>>Ok, this morning I set up the bot so that I could measure the
>>>>
>>>>
>>>voltage to the
>>>
>>>
>>>>motors. When I set the motor speed at 127, the voltage across the
>>>>
>>>>
>>>motor pins
>>>
>>>
>>>>was 8.7, which is pretty reasonable. When I changed the motor speed
>>>>
>>>>
>>>to 120,
>>>
>>>
>>>>the voltage across the pins was just below 1. It held steady around
>>>>
>>>>
>>>0.6V.
>>>
>>>
>>>>That's certainly a bit low for those motors.
>>>>
>>>>The second time I tested this, I got the same voltage at 127, the
>>>>
>>>>
>>>same at
>>>
>>>
>>>>120, about 0.4V at 100, then I tried 126. The voltage first showed
>>>>
>>>>
>>>about 2V,
>>>
>>>
>>>>at which the wheels bumped forward some, but the voltage dropped rapidly
>>>>down to 0.8V.
>>>>
>>>>That's not a very smooth curve. Can you point me towards a solution?
>>>>
>>>>
>>>>
>>>What did you get at the OOPic pin?
>>>
>>>This sounds like the kind of thing that happens when the motor power
>>>supply ground wire is not connected to the logic ground.
>>>
>>>As discussed in another thread a couple of days ago, you need to
>>>create a STAR ground at the motor controller chip. The logic ground
>>>and the motor ground tie individually to that point. The objective is
>>>to keep motor ground current off of the logic ground wire.
>>>
>>>There is a wiring diagram for the L293D (a predecessor to the 754410)
>>>at the bottom of the oDCMotor2 object reference.
>>>
>>>Richard
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>--
>>View this message in context:
>>http://www.nabble.com/H-Bridge-issue...maybe.-tf4867316.html#a13939029
>>Sent from the OOPic mailing list archive at Nabble.com.
>>
>>
>>
>>
>>Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
--
------------------------------------------------------
Dennis Clark ooPIC Tech Support
www.oopic.com
------------------------------------------------------
[Non-text portions of this message have been removed]
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