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BS2 carrier board help — Parallax Forums

BS2 carrier board help

cabcab Posts: 11
edited 2011-09-12 20:34 in BASIC Stamp
Hi
i was hoping someone could point out the difference between the Vss/Vdd bus bars on the BoE Dev board and pins Vss/Vdd on the carrier board. As i have a serial display and an airtronics reciever connected on the BoE board and all works great, using the bus bars. i move the same circuit to the carrier board, soldering the power wires together then the same with the ground wires and both to a servo connecter and slip that onto the carrier board pins, and chop the middle wire that would goto reset. no worky worky.
i can produce the schematic and pics and all if needed, but was hoping it was sumthin obvious.
thanks in advance
Chris

Comments

  • dandreaedandreae Posts: 1,375
    edited 2011-08-23 06:47
    Vss is ground and Vdd is 5 volts. There is no difference except that the BS2 Carrier board doesn't have an external regulator. The BASIC Stamp is only rated for 80mA. I suggest using a 5 volt regulator such as a LM2940.

    Dave
  • cabcab Posts: 11
    edited 2011-08-27 10:46
    ok dave tank you, that makes sense
    so now i have rewired the carrier board and have moved to 5v reg to provide power to everything including the carrier board
    1 amp 5v reg so should be plenty
    so here is my new question
    if i have connected the ground (-) port of the "9 volt plug" on the carrier board to the common ground
    will that be good enough or will i also have to connect pin Vss to the common ground
    considering the motor controllers i am driving need to be connected to the ground of the device that is driving them
    so the motor controller grounds goto the common ground
    so i guess the real question is...
    is the Vss pin the same thing as the (-) port on the 9 volt connector?
  • cabcab Posts: 11
    edited 2011-09-08 19:58
    does anyone know the answer to the vss pin and (-) port on the 9 volt question above
    how about this one...
    i am using a 5v regulator to power the carrier board, a 4x16 serial display and an airtronics reciever
    i am driving two sabertooth motor controllers with the stamp and i have connected the ground from the motor controllers to the ground on the 5v reg
    i connected a 9 volt plug to the 5v+ and the ground and connected it to the carrier board
    the idea is to connect the ground of the motor controllers to the ground of the stamp
    or do i also need to connect a vss pin to this common ground
    a handy bit of info is that the voltage regulatot gets REAL hot
    have i miswired? or is that common
    maybe to many amps?....but i doubt it
    anyway my motor controllers are freaking out
    they listen somewhat but do random things while in the middle of doing what i told it
    everything was workig great then i moved to power from regulator and this!
    help! i am salty at it now
    chris
  • Mike GreenMike Green Posts: 23,101
    edited 2011-09-08 20:28
    Which motor controllers?

    You don't want the common ground to be on the carrier board. You want it to be at the battery or at the motor controller so the heavy currents stay within the battery and motor controller. You then have a Vss (ground) and Vin (unregulated + supply) lead from the battery or motor controller board to the BS2 carrier board. If the regulator is getting hot, you've either wired things incorrectly or you have too much current drain from the regulator. The Stamp and the serial display won't draw much. I have no idea what the receiver draws. You should know that.

    Some of the sabertooth controllers will put out regulated +5V for use by a microcontroller. Will yours do that?

    A schematic will help a lot. Do you have enough bypass / filter capacitors in the right places? Have you wired the regulator properly? There's a lot of crucial stuff you're not telling us.
  • cabcab Posts: 11
    edited 2011-09-09 18:21
    Mike
    i have two 2x25 sabertooths
    http://dimensionengineering.com/Sabertooth2X25.htm
    they will produce 5v but if i run the stamp off of that then the motor controllers have power before the stamp boots up and freak out for 1 second or so
    therefore i would prefer to keep the bs2 power off of the controllers so in the future i will add a switch that turns on power to the controllers after the stamp is booted up
    i have no filters or caps to speak of
    it worked perfectly using the board of education carrier board
    then i moved to the carrier board and needed to add the 5v reg because of amps from the vdd pin were too high
    here is a copy of my schematic.....sorry its kinda sloppy
    maybe i could move the 5v ground of the controllers off of the regulator ground and onto the Vss pin on the bs2?
    im at a loss but i feel certain the issue is somewhere in the 5v reg or ground
    like i said it gets real hot like burn u hot
    thanks for the reply Mike
    Chris
  • cabcab Posts: 11
    edited 2011-09-09 18:24
    oops i forgot my rats nest
    pdf
    pdf
    IMG.pdf
    200K
    IMG.pdf 199.8K
  • Mike GreenMike Green Posts: 23,101
    edited 2011-09-09 18:39
    No wonder the regulator is hot. You're running it off 24V, probably without any significant heatsink. As I mentioned, you've not indicated how much current the receiver draws. The Stamp and display probably total 50mA, more if the display is backlit. Say the receiver draws another 50mA. That's 100mA total with a voltage drop across the regulator of 24V - 5V = 19V. That's about 2W of heat (19V x 0.1A). You need a good heatsink with that much power turned into heat. The regulator is probably shutting itself down to prevent damage from the heat. You would do much better with a switching regulator like those from Dimension Engineering. There's virtually no heat produced, even with a 24V input.

    You do need some bypass capacitors on the input to the regulator and on the output of the regulator. The specific values depend on which regulator you're using. If it's an LM7805, you need a 0.33uF 50V ceramic capacitor on the input of the regulator and both a 0.1uF 50V ceramic capacitor and a 10uF 10V electrolytic capacitor in parallel on the output of the regulator. The capacitors should be mounted within 2 inches of the regulator.
  • cabcab Posts: 11
    edited 2011-09-09 19:01
    mike
    do you have a idea on how to integrate a heat sink
    and what do those caps do and where can i get them
    or better yet is there a better way altogether?
    a dc/dc converter can bring me down to 12v then a 5v reg?
    i am going to need 12v anyway i was just gonna add a 12v reg
    any other ideas?
    thanks
    chris
  • Mike GreenMike Green Posts: 23,101
    edited 2011-09-09 19:16
    I can't answer your questions without more information from you. Most important is the type of regulator you're using. How to mount the heatsink and what capacitor values to use depend on the regulator. The regulator's datasheet usually describes the capacitors it needs and what possible effects the lack of the capacitors may have.

    Dimension Engineering makes adjustable regulators as well that can produce 12V. You need to know how much current will be drawn at 12V. They make a 1A and a 3A regulator. You'll need to use the appropriate one.

    There's likely to be a RadioShack store near you. Go look in their parts area for heatsinks. They have several different kinds. Usually the more fins and the larger the mass of metal, the more heat it can dissipate. You'll also need what's called heatsink compound which they also carry. Read the Wikipedia article on heatsinks for more information and follow the links provided to learn more. RadioShack would also have the capacitors.
  • cabcab Posts: 11
    edited 2011-09-09 19:39
    oh im sorry you had guesses it i am using the lm7805
    i will check the manual
  • Mike GreenMike Green Posts: 23,101
    edited 2011-09-09 19:51
    The LM78xx series regulators are relatively insensitive to the presence of capacitors. Some regulators will oscillate if they're missing ... not the LM78xx. The 0.33uF input capacitor helps when the regulator is more than an inch or so from the power source by smoothing out very high speed brief demands for power. The 0.1uF and 10uF capacitors provide some local regulated power buffering, again for sudden power demands. The 0.1uF handles transients on the order of microseconds or less and the 10uF handles transients on the order of hundreds of microseconds.

    Because the tab of the regulator package is connected to ground, it's pretty easy to attach a heatsink to an LM78xx. Use a thin layer of heatsink compound / grease between the tab and the heatsink and hand tighten (tightly) the screw that holds the regulator to the heatsink.
  • cabcab Posts: 11
    edited 2011-09-10 15:57
    mike
    just wanted to verify that i need the .33uF cap specifically for the input side
    being as radio shack had what seemed to be every cap known to man but that one
    they had .22 or 330 or 3300 but no .33
    and i was able to get everything else there
    thanks
    chris
  • Mike GreenMike Green Posts: 23,101
    edited 2011-09-10 16:14
    I couldn't find something that would work electrically that wasn't physically huge. See if they have a package of 0.1uF 50V capacitors that are small enough and use 2 or 3 in parallel. If you can't find anything, leave it out. There are a lot of mail-order distributors that carry 0.1uF / 0.22uF / 0.33uF values in 50VDC ratings. The 0.1uF particularly is used all over the place in digital circuitry. Get a bag of 100. Look at Jameco, DigiKey, SparkFun, and Mouser for hobbyist-friendly sources of all sorts of electronics stuff.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-09-10 21:45
    Chris,

    Mike has recommended the Dimension Engineering regulators several times here on the forum. I frequently second his suggestion. I've recently had trouble with interference when using Dimension Engineering's switching regulators with wireless projects.

    I don't think there is problem with DE's regulators specifically; the problem is inherent with switching regulators in general.

    One of the projects I've had trouble with was using a Spektrum 2.4GHz helicopter radio. The transmitter and receiver frequently failed to lock on to each other when I used a switching regulator. Other regulators didn't cause this problem. The other project where I think interference from the switching regulator was an issue was a GPS data logging project. The regulator limited the GPS units ability to receive the signals from the GPS satellites.

    I just thought I'd add a warning about this for those who might be considering a switching regulator.

    Duane
  • Mike GreenMike Green Posts: 23,101
    edited 2011-09-10 22:25
    The solution to this sort of problem is to add additional shielding around the regulator and add RF bypassing on the input and output of the regulator. Most modern large amateur radio receivers use switching regulators in their power supplies. The switching regulator is in its own little internal metal box and everything going in or out is bypassed and filtered appropriately for the frequencies involved.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-09-10 23:38
    Mike,

    Thanks for the suggestions. I'll give them a try. I would be very useful to be able to use these switching regulators with the projects I mentioned. They are both battery powered and the switching regulators would really help with battery life.

    Duane
  • cabcab Posts: 11
    edited 2011-09-12 20:34
    Thanks for the info Duane and Mike
    i added the heat sink, but that didnt help
    so i am trying to find all of the caps to add them to my existing regulator
    if that doesnt work, i am moving to a dc/dc converter to 12 volts then a 5v switching reg and i will try to shield it like mike says
    hopefully that will work
    what do you guys think of a chassis ground?
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