Hi There
Can you please tell me if I can operate the big 20 KG thrust servos with your 6channel pololu maesro?
Thank you and I look forward to your kind reply
Joe
Hello, Joe.
I’m not sure what servos you are asking about, but if they respond to the same type of signal that a normal servo responds to then you should be able to control them with a Maestro. They will probably draw a lot of current so you would want to find a way to power them without going through the Maestro’s servo power (VSRV) pins.
–David
Hello again David
Thanks for replying to my question, the servos i want to use are the tower pro 9805bb from hobby king,it says that they are rated at 4.8 to 7.2 v, and have a 20 KG thrust ; I have one of your6 channel maestro and I am operating 3 mini servos with it,I made the bypass as per your instructions and I operate both the pololu and the servos with one power supply ,is it complicated to operate the big servos and the pololu from different power supplies and could you tell me how to do it please?
thanking you in advance
Joe
Hello, Joe.
I looked at the servo you mentioned and I can see now that it’s not as big as I thought. It should be fine to connect it directly into the Maestro, powering it from the Maestro’s servo power rail.
We have explanations of how to connect power and servos to the Maestro here:
pololu.com/docs/0J40/7.a
–David
Hello again David and thanks for replying to my question,I will do it as per instructions
Regards
Joe
Hi David, I did as you said but when, I tried loading a sequence into it , with one 6v- 1200AH battery, the red error led came up and the sequence was all jumbled. However when I attached another 6v battery to the VIN it worked, I am confused as the first battery I mentioned should be more than enough to power them. Why is this and can I do something else, like use only one battery?
-Kind regards
Joe
Hello, Joe.
It sounds like your first battery is not charged enough or is not capable of delivering enough current to power the servo. As a result, the battery voltage is dropping, causing the Maestro to reset.
You should be able to find a single battery or battery pack good enough to power this servo. Unfortunately the current draw of the servo is not listed on the website.
–David
Hi David
Thanks for answering so quickly, I have just tested the battery and it,s reading5.9 Volts,I have put it on charge and I will see what happens with it fully charged,I will let you know how I got on to-morrow
Best regards
Joe
It sounds like it worked with separate batteries for the Maestro and servo? If this is the case, the reason it didn’t work from one battery is voltage sag. A NiCd or NiMH battery near the bottom of capacity will have a large dip in voltage if current is pulled (such as from your servo). The Maestro will not work under a certain voltage, while the servo still does. A charged battery should be able to run the Maestro and servo at the same time.
In higher power applications such as theses, it isn’t uncommon to use separate batteries for servos/motors and control electronics. Sometimes it is just the easier solution.
Hi
The battery that I am using is a lead acid 6v 1200 Ah,which I only bought 2 weeks ago,I have charged it and the voltage read 6.45v but still it was not enough to power the two big servos and the maestro,now I have put a separate supply for it and it works fine, I am sure that it,s the servos fault as I tried smaller ones and the system worked with just one supply,I can,t understand why as with the usb connected to the maestro and a supply to the servos it worked fine as well so obviously the maestro don,t need too much power to operate,any way I will leave it with two supplies unless someone has another solution for me,can anyone tell me how to switch on the maestro by remote control? I was thinking of using a switch pushed on and off by a servo,is there a way I can do it electronically?
Many thanks
Joe
Hello, Joe.
I think you mean 1200 mAh (milliamp hours). Do you know what the discharge rate of the battery is? If it is 1C, that means it can only supply at most 1200 mA, which would be too small because each of those servos could easily draw more than an amp when starting up.
By connecting a different battery to VIN, or powering the Maestro from USB and disconnecting VIN, the Maestro’s microcontroller is able to keep running even when the voltage on your main battery dips.
Why do you want to switch off the Maestro? Are you trying to conserve battery power? How is the Maestro controlled (e.g. internal script, serial commands, USB commands)?
–David
Hi Dave
The servos I,m using are the turnigy S8166m (two of them), the writing on the battery says it,s 6v12AH/20HR, The maestro is controlled by USB commands,I am using it on a 1/6 scale Tank, I am using only two channels from it, I,m using it to simulate the cannon firing, command 1 fires the cannon and command 2 does the recoil action,the reason I want to switch it on and off at will is so that i can fire the cannon when I want to because if I leave the maestro on, it will repeat the sequence and i don,t want that,like i said I was thinking of just doing it mechanically by operating a servo to switch the maestro on ,it would be great it i can do it electronically tho ,do you have any ideas how?
Many thanks
Joe
Thanks for the details, and this sounds like a cool project. It would be great to see videos when you are done with it!
Since you’re going to have the USB cable connected to the Maestro, you probably won’t need to have a second battery connected to VIN. You should leave VIN disconnected. Then the Maestro can be powered off of USB and be hopefully be immune to the battery voltage dips that happen when you drive your servos.
Rather than make a mechanical system to make the Maestro to stop firing, you should just program it to stop firing. You’re using the Maestro’s internal scripting, right? Just add a “quit” command at the right place to terminate the script.
–David
Hi Dave
I am afraid I do not know what you are talking about as my son does all the programming on it,but I will not have the USB cable connected to it, as the maestro is in it the tank,and the tank is remote controlled, what I want to do is to press a switch on the transmitter which will switch on the maestro and the cannon will fire once, everytime i want to fire the cannon I have to switch the maestro on to start the sequence,instead of using a servo to switch on the maestro ,I thought maybe i do somthing like for example pololu item752 ,it receives the signal from the radio and switches on the maestro,what do you think?
Many thanks
Joe
Yes, you might be able to use our RC switch with digital output to power on the Maestro, but I think it would be better to keep the Maestro powered all the time and just connect the digital output of the RC switch to a channel of the Maestro that has been configured as an input. Then your son can write a script that waits for the input to go high, and when it goes high it performs the motion sequence and then goes back to waiting. One advantage of this is that the Maestro will never get powered off in the middle of its motion sequence.
–David
Hi Dave
Ok I will get one of these switches and let you know how i got on
Many thanks
Joe