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Matco ASK2008TR Power Question (Hexcrawler) — Parallax Forums

Matco ASK2008TR Power Question (Hexcrawler)

DonWDonW Posts: 37
edited 2006-01-17 02:42 in Robotics
Finally....putting the finishing touches on the Hexcrawler remote control project (using the Tower Hobbies RC system). Using the Matco ASK-2008-TR and a Matco CNL-100-C camera.

One minor obstacle, which surprised me. The docs I have show the transmitter/camera being run from the two rechargeable batteries...spec on the unit is 12-15V, and if you assume two 7.2V batteries, one would think they are fine.

Long story short..I did that, and some heat, and a little smoke, as the batteries, even under servo/BOE load, along with the camera/xmitter unit, still hits about 16V, with I'm sure plenty of current, and I'm assuming that is my problem. (No damage to the xmitter board, or the camera, but I was sweating a bit..)..

Curious if anyone has had the same issue, and/or, how tolerant they have seen the unit at the 15-16V level.

And..looking for recommendations for power options...thinking about..

1. just another small rechargeable battery, 12V, though, hate to add any more batteries to charge.

2. a small 12V regulator (essentially, a DC-DC converter), 15V in, 12V out.

Open to other ideas, and/or part/source recommendations for option 2. Mouser has a few that aappear they may work, but I always find the best ideas are right here on this forum.

Thanks!

Comments

  • denodeno Posts: 242
    edited 2006-01-05 14:08
    Hello...Pictured at the left is ROBO CHILD and I use the same transmitter and receiver from Matco. (Actually, I also use the 1 watt power amp for more range as well).

    The transmitter unit (before I added the power amp) was running on 13 volts.

    The camera however, is a different story.· Somewhere in the paperwork on my board camera from Matco, I was told not to exceed 10 volts.· In reading the new documentation on Matco's web site, I see that they are posting 13 volts max???· Anyway, my camera works just fine on 10 volts.· I just built a variable voltage supply using a LM317 and a multiturn pot to trim the voltage down to 10 volts max.

    What exactly got hot...something on the camera or the transmitter board?

    Deno
  • DonWDonW Posts: 37
    edited 2006-01-05 14:49
    The transmitter unit was warming up...

    An LM317 would work...curious if the single chip DC-DC converters might work also..or whether they would need just as many external components...

    The bot looks cool!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-01-05 15:19
    Don,

    ·· The article you referred to had the batteries in series/parallel.· What this means is that the series connection of 14.4V was used to power the camera (Which was designed to handle that voltage), but the servo power was tapped off one battery only, supplying 7.2V to the servos.·

    ·· I am currently in the process of revising that article.· I am just waiting for a new camera which will run on a lower voltage.· One that arrives I will be posting a revised edition of that document which runs only on one 7.2V battery pack, with the camera possibly running off a separate pack to isolate it from the servos.· Stay tuned.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • DonWDonW Posts: 37
    edited 2006-01-05 15:41
    Right..there is no issue with the wiring..(other than some wacky things I noticed with the SSCs and grounding the servo ground and SSC ground..but that's a non-issue and another story..)..

    Anyway..issue is..those 7.2V batteries, fully charged, even under load, give me a solid 8V (times 2), so we have 16V going to the transmitter/camera.

    The idea of a separate regulator circuit, either LM317 based, or using one of the DC-DC converter chips, makes sense.

    Re the camera you are waiting on..is that also a transmitter that also runs on lower supply voltages?...even with a 6 or 9V camera, that only fixes part of the "problem"..

    Do tell.. smile.gif
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-01-05 16:52
    Regulating the voltage for the camera won't be a big issue.· Trying to regulate the voltage to the servo is another story.· The cameras I am looking at are listed as battery powered.· They are also from Matco, but normal cameras run from 12V, whereas the ones I am looking at run from either a regulated 5V or from 4-9V.· The 5V ones could actually be run from the VDD output of the BOE.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • DonWDonW Posts: 37
    edited 2006-01-17 02:42
    Robotic egg on my face on this one..

    Built an LM317 regulator circuit...hooked it up..and still saw smoke...ground wire on the transmitter unit melting..

    Took a step back, noticed the 7812 regulator on the board, and realized there ain't no way this was a "too much input voltage" kind of thing.

    Removed transmitter unit from robot base, tested with LM317, worked fine..

    Reinstalled...worked fine..

    The only thing I can think of is I had some sort of short, somewhere, to the base of the robot...for the life of me, I can't see where, and the board sits in the same place it did when it was melting down..
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