Well my long awaited order arrived, but silly me I did not order batteries. I am flipping through the SSC-32 manual and it says for the VL=VS jumper:
however, below it, I see
I am using 7 HS-422 servos for this project. Is using a 9v battery safe? I think I’ve got a nimh 9v (actual 7.2v IIRC?) kicking around someplace. And which terminal am I wanting to hook the battery into to run both servos and logic?
edit: I actually have an adjustable walwart and the wiring harnass that came with the robot arm base. I have an adjustable wall wort that can spit out anywhere from 3 to 12v in 1.5v increments. This means I cant hit the magic 7.2 but I can hit 6 or 7.5, or 9 or 12 for that matter. I am new to the ssc-32 and am looking to set up a one connection solution, that will power both servos and logic from one of my available voltages. Can it be done, if so which voltage is best and on what set of screw terminals? I am looking to power only 7 servos now, but would like the option of using all 32 later on when I expand my project. I just dont want to end up frying the logic trying to give the servo bus enough power.
The VS/VL (Voltage Servos/ Voltage Logic) jumper is to allows the electronics to be powered off a separate power supply from the servos. The SCC-32 needs only 5V to run.
The reason this is here is because when using a 6.0V or 7.2V battery (RC pack) and drawing really high current, the voltage could go under 5V briefly and your electronics would reset, causing a lot of problems. Also if you really wanted to run at 4.8V exactly you’d need to supply a secondary 5V source for the electronics.
If you have a wall supply, i.e. more current than you expect to ever draw with your servos, and want to run the servos at 5V or higher, you can safely just select VS, power everything off the one power supply and forget about it. In your case with the adjustable unit, I would set the switch to 6.0V. Using a single 9V battery to power everything is not really possible since the servos will draw far too much current. You need a decent pack or wall supply.
For your information, Hitec servos can be overvolted rather safely. I believe somewhere on the forum or main site Jim shows HS-422s running on much higher voltages. Since most RC packs when fully charged are in the 8V range, I don’t think going at 9V (if you had an appropriate current source at 9V) would necessarily hurt. However, unless you really have a need for this (servos get stronger with more voltage) I won’t risk it. Also, the SCC-32 has a regulator that can handle anything from a bit over 5V to a bit over 12V just fine. The manual simplifies this since besides an RC battery pack (which one would use for the servos) the only common battery in the range is a 9V.
Thanks for the reply. Ya, I figured out most of this after originally posting, then going to look over the manual for the SSC. About ten minutes looking over the schematic (hey, I’m rusty) and I understood what the VS jumpers were doing. I am stuck using a 9v battery (not pack, sandard energizer 9v battery) to power things. My wallpack wiring harness is no longer working. I dont have a multimeter to be sure but I suspect I broke the switch itnernally. A replacement is being ordered.
I’m still not sure about the servo move command. When I issue it, the servos jerk and then stop before reachign the destination I set, almost like they are only getting one pulse. Is there an argument I need to set beside the pulse width? Or could it be that trying to drive the logic plus a servo off a single 9v is pulling the SSC into a reset every time I give a command?
Servos take a lot of power, so trying to run them off of a 9v enregizer battery is somewhat like trying to jump start your car off of that battery. You need a larger battery pack or AC powered power supply until you get your project worked out.
Yea, a quick search shows most 9V batteries are rated 160-400 mAh.
Your electronics draw close to 250 mA alone at 5V. Most alkalines aren’t really designed to be drawn at 1C.
Remembering to compensate that your logic actually draws less at 9V, (since the regulator is a switcher) the SCC-32 is drawing close to 1C by itself. If you have a heavy duty 9V or a type that can comfortably provide a few C, you might have enough juice for a couple of servos (nowhere near 7). However, many NiMH 9V are at the 160 mAh end of things since they can be drawn at 2C.
I’d try just connecting one servo to test your interface ( though even that still might not work for power reasons) it at least has a better chance to allow you to debug and lets you make some progress till your replacement power supply comes.
However, long story short, you need a decent power pack. I personally have the 1600 mAh 7.2V pack Lynx sells and can say that it works well enough for my 12 Hitec 5955s; and those servos draw a lot of current.
