## Roboard and Capacitor

Based on DMP's Vortex processor / SoC this board is a full computer capable of running a standard Windows and Linux installation on the backpack of your robot.
3 postsPage 1 of 1
3 postsPage 1 of 1

### Roboard and Capacitor

I am working on a new torso design for my bioloid and since I have to fit quite a number of items in a small space, I was thinking of adding a capacitor between the battery and roboard so that it might serve as a protection in case of loose contact, of coarse to avoid burning my dear roboard. Now I am a complete newbie as regards electronics, anyone can suggest whether this is a good idea, and if so what is the size (uF) for the capacitor? also can a fuse be used as a protection against reverse polarity?

Thanks
I am working on a new torso design for my bioloid and since I have to fit quite a number of items in a small space, I was thinking of adding a capacitor between the battery and roboard so that it might serve as a protection in case of loose contact, of coarse to avoid burning my dear roboard. Now I am a complete newbie as regards electronics, anyone can suggest whether this is a good idea, and if so what is the size (uF) for the capacitor? also can a fuse be used as a protection against reverse polarity?

Thanks
F'dan il-passatemp ghandek bzonn zewg affarijiet - FLUS u HIN. Zewg affarijiet li huma skarsi hafna u li jien minnhom ghandi vera ftit!
JavaRN offline
Savvy Roboteer

Posts: 282
Joined: Fri Mar 02, 2007 11:01 pm

Hey Java,

I have a few recommendations:

If you have the potential for loose contact, you will have problems regardless of a capacitor.

It would take a decent sized capacitor (I forget the math, the formula is on the 'net, R/C time constant formula). You have a load (Roboard @ 500 mA, 6V minimum in, 12 ohm "perceived / calculated" load), then you just need to know how long you want to sustain the load (how much the voltage can allowably drop), which will tell you how many uF's you need. Rate your cap at > 6v (or > whatever your source voltage is).

With loose contacts, chances are, current handling and resistance in the connection will cause problems. Arcing and sparking will cause carbon buildup, which will cause an increase in resistance the more the connection "jitters".

Losing power to Roboard shouldn't cause it to fail outright, but it might scramble the hard drive (microSD card) data if reading or writing during the power loss.

Your best bet is to use good connectors, and good wire. I like the silicone high strand count stuff where flexibility is required.

Protecting against polarity reversal is easy, just use polarized connectors that can not mechanically get plugged in wrong, and always check, check, and re-check when adding such connectors (new battery packs, etc).

Don't use a fuse, it probably won't act quick enough. Semiconductors pop fast.

Take Care,
Paul
Hey Java,

I have a few recommendations:

If you have the potential for loose contact, you will have problems regardless of a capacitor.

It would take a decent sized capacitor (I forget the math, the formula is on the 'net, R/C time constant formula). You have a load (Roboard @ 500 mA, 6V minimum in, 12 ohm "perceived / calculated" load), then you just need to know how long you want to sustain the load (how much the voltage can allowably drop), which will tell you how many uF's you need. Rate your cap at > 6v (or > whatever your source voltage is).

With loose contacts, chances are, current handling and resistance in the connection will cause problems. Arcing and sparking will cause carbon buildup, which will cause an increase in resistance the more the connection "jitters".

Losing power to Roboard shouldn't cause it to fail outright, but it might scramble the hard drive (microSD card) data if reading or writing during the power loss.

Your best bet is to use good connectors, and good wire. I like the silicone high strand count stuff where flexibility is required.

Protecting against polarity reversal is easy, just use polarized connectors that can not mechanically get plugged in wrong, and always check, check, and re-check when adding such connectors (new battery packs, etc).

Don't use a fuse, it probably won't act quick enough. Semiconductors pop fast.

Take Care,
Paul
PaulL offline
Savvy Roboteer
Posts: 423
Joined: Sat Sep 15, 2007 12:52 am

Thanks Paul!
Thanks Paul!
F'dan il-passatemp ghandek bzonn zewg affarijiet - FLUS u HIN. Zewg affarijiet li huma skarsi hafna u li jien minnhom ghandi vera ftit!
JavaRN offline
Savvy Roboteer

Posts: 282
Joined: Fri Mar 02, 2007 11:01 pm

3 postsPage 1 of 1
3 postsPage 1 of 1