Shop OBEX P1 Docs P2 Docs Learn Events
Power Light on BOE dims then brightens — Parallax Forums

Power Light on BOE dims then brightens

TheBoyRobotTheBoyRobot Posts: 1
edited 2006-07-08 17:58 in Learn with BlocklyProp
HI guy's/girl's
I have a question. Whenever my servo horn moves, the power light on my BOE kinda gets dim then brightens back up. Is this because it is pulling power from the power source? ( 9 volt battery). It does then if I set the jumper to vin and vdd, although it does not get as dim when the jumper is set to vin.

Post Edited (TheBoyRobot) : 6/25/2006 4:17:55 PM GMT

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2006-06-25 20:02
    A 9-volt battery may be too much for a servo.

    What's happening is that the servo takes a lot more current than the BS2 (100 mA versus 5 mA). Thus, when the servo moves, the additional current drawn may lower the output voltage of the 9-volt battery (due to the 9-volt's internal resistance). This can dim the power LED on the BOE board.

    It can also 'reset' the BS2 on the BOE board.

    Now, if you set the jumper to "Vdd", then the servo is being powered from the 5-volt line. This means ALL the servo current goes through the regulator. When you set the jumper to "Vin", then the servo current bypasses the regulator. It probably takes a little more current at 5 volts to move the servo than it does at 9 volts.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-06-26 01:31
    allanlane5 said...(trimmed)
    A 9-volt battery may be too much for a servo.
    Allan,

    ·· Did you perhaps mean the servo is too much for the 9V battery?· =)

    TBR,

    ·· A 9V battery is certainly not recommended for any long-term running of the servo, not only because the current draw is too much for the battery, but also because the 9V is high enough to cause excessive wear on the servo.· A 4AA battery pack supplying around 6V should work nicely.· It's what we use on many of our Robots.· I hope this helps.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-07-08 17:58
    Also the capacity of a single 9V battery is much less than 4 1.5V AA batteries. If you split open a 9V battery you'll see 6 very small individual cells that are the same as the (rare) AAAA batteries. These have less capacity and therefore last a much shorter period of time.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Life is one giant teacup ride.
Sign In or Register to comment.