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Working on Servo/Sensor board for Propeller Platform: Comments requested — Parallax Forums

Working on Servo/Sensor board for Propeller Platform: Comments requested

Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
edited 2012-02-10 16:41 in Propeller 1
Admittedly, I'm still a greenhorn when it comes to Diptrace, but I figure if you don't jump in the water, you never learn to swim..

I'm working on a servo/sensor board (see attached) and would appreciate comments.

Yes, I know there are a couple traces I need to tie into the cooper pour (still looking for that).

I've placed a SOIC-8 breakout on this, but am starting to doubt this would be the handiest to have. Ideas?

Add thick 5v traces all around. Still needs copper pour to GND, cap pads?

servo_sensor_revDf.JPG
servo_sensor_revDb.JPG


OBC
servo_sensor_revDb.JPG
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servo_sensor_revDf.JPG
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Comments

  • pedwardpedward Posts: 1,642
    edited 2012-02-08 17:23
    Right click on the pad and select the "tied to plane" or somesuch, then select the top or bottom, whichever is correct. You can also specify the type of pad as "thermal", which makes it an island with 4 bridges, so the pad can be soldered easier.

    EDIT: I see you have a SOIC breakout there, I think it would be neat to make a shield that has several SMT packages on it as a breakout/protoboard. You'd have an SMT area and PTH area on the same board.
  • John AbshierJohn Abshier Posts: 1,116
    edited 2012-02-08 18:58
    To drive servos, I often use Vin.

    John Abshier
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-08 19:32
    What is a servo? This forum sounded interesting so I thought I'd ask, and maybe jump in the pool and swim with you guys! (get it.....:lol:)
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-08 19:35
    Looking at it, it looks like a mount that the propeller works with some other kind of chip, and controls sensors. Would that slot in the upper left hand corner be where the servo goes?
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-08 20:29
    Nah, The servos and sensors plug into the end of the right side.

    There are three jumpers: (two decide power options 3v or 5v for each row of 8, the center jumper allows connection from a single power jumper to cross all 16 connections. Removing the center jumper allows you to have a row of 3v items, and a row of 5v items.

    The connections on the left are something I thought would be handy for linking the board to another PCB or breadboard.

    OBC
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 04:42
    I was looking up what a SOIC-8, and all found was the dimensions of an 8 pin small outline integrated circuit. I know this is what SOIC-8 stand for, but is this a kind of OPamp, a logic gate, a timer chip, or a specialized chip like a memory one. But back to the top, i was reading about this SOIC-8, and one person wrote it as a waste of time and money. I guess he didn't like it very well.
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 04:48
    If it's for sensors, you couldn't go wrong with an and, an or, and a not gate, plus a few photoresistors, potenmeters, and temperature sensor. I know the logic boards I used in my IT class was setup like that, and we used it for various sensory tests.
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-02-09 07:50
    SOIC-8 is only a footprint. The SOIC-8 pinout on the edge is to lay down any 8-pin SOIC you want and use it with a through-hole circuit.
  • JonnyMacJonnyMac Posts: 9,197
    edited 2012-02-09 08:07
    I would suggest you seriously beef up the traces between the 5v connection and the servo headers; some servos can draw up to half an amp. Also, a couple of BOCs (big 'ol capacitors) will help handle the surge currents imposed by servos.
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 08:07
    That's what I read, but when I searched it some of the things that came up were from fairchild about actual ICs, so I was confused. Thanks for clarifying.
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 08:12
    On my propeller education kit, the breadboard uses two 1000uf capaictors, and has a +9v current dropped down to +5v with a MOSFET, so I think some 1000uf capacitors would help with that. I can also get the MOSFETs I used too if that helps.
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 09:27
    JonnyMac wrote: »
    I would suggest you seriously beef up the traces between the 5v connection and the servo headers; some servos can draw up to half an amp. Also, a couple of BOCs (big 'ol capacitors) will help handle the surge currents imposed by servos.

    Traces...I couldn't agree more.. It's already on my todo list. I ran out of room on the top side and will move expanded traces to the bottom on the next revision. (sometime today).

    BOC's.. I hadn't thought of that! Couldn't they side across one of the pin header positions between R & B when required, or would you consider them to be standard and work in a couple BOC points near the 5v/3v jumpers?

    OBC
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 11:53
    Added thick traces anywhere that 5v could be used for a servo. (updated in top thread)

    I'm "almost" happy with this design, got a couple more issues work out.

    OBC
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 12:08
    Great job Jeff! What other issues are being fixed on your servo?
  • PublisonPublison Posts: 12,366
    edited 2012-02-09 13:04
    SONIC the Hedgehog wrote: »
    On my propeller education kit, the breadboard uses two 1000uf capaictors, and has a +9v current dropped down to +5v with a MOSFET, so I think some 1000uf capacitors would help with that. I can also get the MOSFETs I used too if that helps.

    Those are voltage regulators, and they drop voltage, not current.
  • PublisonPublison Posts: 12,366
    edited 2012-02-09 13:08
    Oldbitcollector (Jeff) wrote: »
    Added thick traces anywhere that 5v could be used for a servo. (updated in top thread)

    I'm "almost" happy with this design, got a couple more issues work out.

    OBC

    Looks like you have some room to fatten up the V33 supply lines also. Just for giggles.

    Jim
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 13:39
    Well yeah, but I didn't know if that would help or not, and if your talking about big 'ol capacitors, I know that I used some 1000uf ones if that helps any. I guess since your talking aout current they wouldn't be necessary, but I've got a feeling about those capacitors.
  • pedwardpedward Posts: 1,642
    edited 2012-02-09 14:21
    OBC, do you have a template for the GG PP in DipTrace, so others have a template to start from to make shields for it?
  • PublisonPublison Posts: 12,366
    edited 2012-02-09 15:17
    SONIC the Hedgehog wrote: »
    Well yeah, but I didn't know if that would help or not, and if your talking about big 'ol capacitors, I know that I used some 1000uf ones if that helps any. I guess since your talking aout current they wouldn't be necessary, but I've got a feeling about those capacitors.

    Hey Sonic,

    It would be great to use the "Reply with Quote" to be sure which reply you are addressing.

    Just sayin'

    Jim
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-02-09 15:28
    John Abshier wrote: »
    To drive servos, I often use Vin.

    John Abshier

    I second John's Vin request.

    You could make the jumper have three possible positions by placing a hole to the outside of each center hole. Right between the "V5" and "V3" silkscreens.
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 15:37
    pedward wrote: »
    OBC, do you have a template for the GG PP in DipTrace, so others have a template to start from to make shields for it?

    Yes, when it's finished I'll make the design Open Source. :)

    OBC
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 15:56
    Duane Degn wrote: »
    I second John's Vin request.

    You could make the jumper have three possible positions by placing a hole to the outside of each center hole. Right between the "V5" and "V3" silkscreens.

    I'm starting to run out of room for these thick traces, but something like this?

    servo_sensor_revF.JPG


    OBC
    servo_sensor_revF.JPG
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  • pedwardpedward Posts: 1,642
    edited 2012-02-09 16:01
    What does the bottom look like, can you put 3p3 on the bottom layer?
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 16:09
    pedward wrote: »
    OBC, do you have a template for the GG PP in DipTrace, so others have a template to start from to make shields for it?

    BTW, this is the template I started with... The .dip file is near the bottom of the page in the resources section.
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 16:10
    pedward wrote: »
    What does the bottom look like, can you put 3p3 on the bottom layer?

    Still playing with it, but I've got a lot of nice I/O traces on the bottom I don't want to sacrifice..

    OBC
  • John AbshierJohn Abshier Posts: 1,116
    edited 2012-02-09 16:14
    Looks OK.

    John Abshier
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 16:16
    John Abshier wrote: »
    Looks OK.

    John Abshier

    Yeah, my thinking too.. I'll keep fiddling with it until I find "elegant" :)

    OBC
  • SONIC the HedgehogSONIC the Hedgehog Posts: 321
    edited 2012-02-09 16:28
    Publison wrote: »
    Originally Posted by SONIC the Hedgehog
    Well yeah, but I didn't know if that would help or not, and if your talking about big 'ol capacitors, I know that I used some 1000uf ones if that helps any. I guess since your talking aout current they wouldn't be necessary, but I've got a feeling about those capacitors.
    Hey Sonic,

    It would be great to use the "Reply with Quote" to be sure which reply you are addressing.

    Just sayin'

    Jim
    Sure thing! But seriously though I will be sure to do so.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-02-09 16:28
    OBC,

    Here are some of my ideas (just keep in mind I have less circuit board designing experience than you). I like the SOIC idea; what about expanding on it? If you stagger the 0.1" holes (or just route the traces around the inner hole, you could a section to add multiple SOIC chips. This way one could add different combinations of SOIC chips, each having different amounts of pins.

    I drew my guess at traces for the power lines (I drew only one side, but if you think it could work, you could do the same thing on both sides). I don't know if it's okay to run a line around the outside edge of not.
    servo_sensor_revDf_dwd.png

    Now, that I've thought about this a bit, I think your idea (of having a jumper on the left side of the board too) is probably better.
    servo_sensor_revDf_dwd.png
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  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-02-09 17:19
    Yes, I was thinking about expanding that SOIC somehow..

    It might be time to "flip" the entire design.


    servo_sensor_flipped.JPG


    OBC
    servo_sensor_flipped.JPG
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