So I guess what I did was correct to have delay(15~25) after sneding command to every servo in each loop? Maybe the longer the safer?
I just use my lunch time to grab few 1N5408s and gonna wire them up tonite.
May I ask one more stupid question? Since I am testing the code, what’s best or proper setting for electronics? The bot itself using one battery for both Arduino and Servo shield.
Have USB and power on as always;
Have battery switch off and USB pluged, after uploading trun the switch on;
pull off USB after uploading then trun switch on; or
the proper way you have in mind, please let me know.
I was thinking, could that be the reason causing those servos death because of I did on&off&on&off frequently with USB connected that cause some where impact or conflict? Or this is totally idiot thought that I shouldn’t be worry about this problem?
i think if the is no servo running then the battery voltage maybe higher than 7.2 ( as you tell 8.4V). switching this voltage ON and OFF may damage the electronic circuit inside the servo. I think this fault has no relation with the USB power. it is some form of transient voltages. there are some switch mode regulators that could be useful for you see this for example (http://www.radicalrc.com/category/Voltage-Regulators-86). this will eliminate the need for the diodes also.
This is what I did for 2 1N5408 diodes as shown in picture. The voltage was 8.3V without diodes.
Is this the number I should get? Hopefully the image is clear enough. The Battery is 7.4V 2 cell for sure. So just wondering if this is normal the battery reads always higher than what it should be?
The voltage of a Li-poly cell varies from about 2.7 V (discharged) to about 4.23 V (fully charged).During discharge on load, the load has to be removed as soon as the voltage drops below approximately 3.0 V per cell (used in a series combination), or else the battery will subsequently no longer accept a full charge and may experience problems holding voltage under load.
so your battery voltage expected to be 8.46 when fully charged and drop to min 6.0V (you should disconnect the battery at this voltage). so your readings are correct.
simply you can add more diodes in series to reduce the voltage farther.
So I was thinking 3 diodes should do it? Drop down to 6.3V when fully charged?
Correct me if I am wrong, one of my friend told me that regular servo should be working in range of ±1V. That’s why I didn’t do anything to reduce voltage because of I thought my battery was 7.2V and it’s actually 8.4V. Over 2.4V could kill servos easily I think . Especially HS-425HB, other HS-645MG are stronger because I use same battery and same setting for hexapod and they still running fine. But I think I will add 2 diodes on it to prevent further tragedy.
yes this is an easy solution but with limited performance. adding diodes this way will waste power and will decrease battery voltage in all cases. if the minimum voltage to operate the servo is 4.8V then the min usable battery voltage is 6.9V (not 6.0V) so this will reduce the battery operation time.
it costs around 21$. it is more expensive than diodes but it is more efficient than diodes. this will give you 5-6V(adjustable) at the output for input voltages from 5.5V to 42V. some types can handle up to 10A look nice to me in china we could find cheaper
I will see if I can grab one from local hobby store on my way home. Will let you know if it works.
Something confuse me too: The wire from battery is 4x thicker than these switch regulator, it won’t effect the voltage in between? Instinctlly, thicker wire down to thinner wire will heat up the thin wire; other hand, thinner goes to thicker will lose some power? Punch me if I am totally wrong
OK! Got that switch regulator connected. Everything looks perfect now. Hope that will eliminate the problem of SERVO KILLER!! and time to move on IK programming. Arrrrrr…I think that’s another bigger problem now. I do really learned from you guys!! BIG THANKS!!
look nice to me in china we could find cheaper