separate power supply for motor(servos) and BS2...
celestino_galan
Posts: 44
I have read in different places that is allowed to use one power supply for the motors (servos...) and other power supply for the BS2 and sensors...
¿What do you think?
Is not better to have the same battery pack for all?
I say that in order to "charge" the batteries... (Sould we charge the two batteries? isn't it more complicated?)
Thank you
¿What do you think?
Is not better to have the same battery pack for all?
I say that in order to "charge" the batteries... (Sould we charge the two batteries? isn't it more complicated?)
Thank you
Comments
An additional reason is batteries supplying current greater than they were designed for will experience a voltage sag, if this sag drops below the brownout voltage of the stamp, it will reset. This means even though the batteries have enough charge on them to continue operating the bot, it cant be utilized because the stamp keeps reseting due to overdrawing the batteries. Since the servos are the biggest culprit for this and they are less sensitive to sagging voltages, people choose to supply them with thier own power source.
·· It is better to have more than one power supply if the supply voltage is close to the operating voltage of the Stamp Module and/or Motors/Servos are drawing large amounts of current in spikes (Sudden surges of current).· This can cause the Stamp Module to brownout due to voltage dropping.· In this case separate power supplies helps, although you must have a common ground (Unless the devices are electrically isolated).
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Chris Savage
Parallax Tech Support
csavage@parallax.com
The other problem is if you go through the BOE regulator, it is limited to 1 Amp total. And you can exceed this with enough Servo's, again needing another supply.
However, for what you want, an RC battery pack with regulator driving both the Servo's and the BS2 should work.
Allanlane5: " ....RC battery pack with regulator... "
What do you mean with regulator?
for the servos?
for the BS2?
for both?
Wich one do you recomend me?
Thanks
The BS2 'Vin' pin allows you to drive the BS2 from 7 to 16 volts, so that's not a problem. Definitely put a largish (20 uF to 100 uF) capacitor across the BS2 'Vin' to Vss pins to shield it from short brown-outs caused by turning on Servos.
So, if you can get a 6-volt to 7.2 volt RC Car battery, you can drive your Servo voltage directly with that, and drive the BS2 'Vin' pin with that, and you won't need an additional regulator. I believe the BS2 on-module regulator is a low-drop-out type -- meaning as long as the input is 0.5 volts above the 5-volts output, the regulator will work. Parallax might confirm that.
If you want to drive your Servo's with 5 volts, you'll need an external regulator to do that.
·· I haven't actually gotten them and tried it yet to see how good it works, but on my Hex Crawler (Still waiting to be given life) I am planning on using 2 BARREL diodes to drop approximately 1.4V from the 7.2V R/C Pack.· I don't wish to take any life away from my servos.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Thanks
·· Essentially each diode (Depends on the Diode) will drop a voltage across it.· Barrel diodes are just an example of a higher current handling Diode.· But after looking at the a few I see some actually drop 1.2V across them, so only one would be required.
·· Most Silicon Diodes drop about .7V, while most Germanium Diodes· drop about .2V.· So there is some variance out there.· I guess you could say electronics is not an exact science!···· You gotta do a little research.
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Chris Savage
Parallax Tech Support
csavage@parallax.com