I know 9volts is the specified “MAX” voltage for logic power, but can it go a little over?
I have a power supply that is rated @ 9v, but when I measure the actual output, it shows about 13 volts. Will this damage the SSC-32? I used it for VL power on the SSC-32 and I randomly checked how hot the Vreg was getting and it was only slightly warm to the touch, even after an hour.
With an unregulated transformer, the voltage will read significantly higher in an unloaded state than in a loaded state. Measure it with nothing attached, and compare that reading to the one you get when it’s connected to something that’s drawing something close to its maximum rated current.
When you hook your supply to the SSC-32 you may not see 9 volts, but you’ll probably see something closer to it than 13.
I will give this a shot when I get home today.
Thanks Seamus.
Odds are the MAX VLogic specification is to limit power dissipation of the LM2937 to a safe operating point.
Why? Examining the SSC-32 schematic on page 14 of lynxmotion.com/images/data/ssc-32.pdf the only thing that appears to be operating from/across the VLogic net is capacitor C13 and the LM2937 regulator. The LM2937 is specified for max. operating input of 26V, but you need to keep in mind your power dissipation goes up linearly with the supply voltage. The 9V limit may be back calculated to limit the power dissipation of the TO-263 package from the VCC supply current level. Remember there is no heatsink on the LM2937 so it’s ability to get rid of heat is severely limited. The other limitation might be the rated working voltage of C13, which “could” be as low as 10V and is not specified on the schematic. A fresh 9V alkaline battery however could be putting out as much as 10.5V so I think it is much more likely that C13 would be at least a 16V part.
Oh yeah, if your power supply is a wall wart then how much over the rated output it is will depend on how much current it is rated to supply. Drawing 250mA from a 9V 500mA wall wall wart will load it down to 9V region much easier than a 9V 3000mA one. Also keep in mind that typical wall warts are not especially well filtered DC so you will likely see a lot of ripple riding on the output as you load it down. If you are powering something audio-ish this might show up as 100/120Hz hum.
I have a collection of power wall adapters and I found this one in my closet. Its a toy adapter that is rated for 9v but I did not think to look at the rated current output.
I wil have to give this a look tonight.
I wish they would wire everything in 6 or 12v u cant find large 9v batterys
its 9.6 (13v) OR 7.2V I would just go with 7.2
The main problem here is that the linear regulators basicly turn the extra power into heat. If you are running just the logic through it, it should not have a problem, however you will be using a lot more power than necesary.
I assume you’re not using the same power supply for your servo motors? There would be a problem with that as they are not rated for anything that high.
A 5 or 6 volt power supply would be better if you have one. But, the voltage regulator should have a thermal cut-off, so what you have will do if you don’t mind using the extra power.
Steve
Steve,
Yeah, i’m using 6v for the servo banks (VS) and was going to use 9v for the ABB (VL) input. Id rather use 6.5 or 7v but I don’t have anything that can supply that… well I do have a switchable supply but it only puts out a max of 300mA.
I looked at my wall adaptor last night and it was rated 9v @ 1000mA. It also said open circuit is 13v max.
What I am tring to do is get a reliable supply so I don’t have to worry about recharging batteries. Basically, I don’t have the proper adapters 
Why don’t you use the same 6v for the logic? Also, the SSC-32 only has a few components, so the current required is quite low. It really shouldn’t want 300mA or more.
I haven’t tested it, but I wouldn’t expect it to get above 200mA. Let me know if you want me to test mine and I can for you.
Either way, the 9v adaptor you are using should be fine if you want to use it.
Thanks Steve,
I was trying to figure out why my servo is not operating like it should. I’m thnking it is my wall adaptor is not puting out a steady supply (the switchable adaptor).
I will try Jim’s suggestion previously, and post my results. I know the 9v adaptor is good so I will try that one. It’s possible my old switchable is on its last days. I had weird issues with my stamp board as well.
I will also pick up a fresh 9v battery and see what happens.
EDIT
I forgot to mention that I need to make changes to my code as well, My pauses are to short.
I had problems with my SSC-32 at first. It turned out when I moved my servos fast, the power supply dipped and the servo controller stopped working. It didn’t reset, but it just stopped working, so I had to use separate power supplies. I think the servos can spike with a very high current when they start moving, so this is probably where most problems start. Don’t know if this has anything to do with your problem, but I thought I’d put it up just in case.
Steve
Thanks Steve,
I appreciate your help. I think this is exactly my problem. The servos are drawing more than the supply can handle. I need to not only split the power but get the right power source for the job.
You can always switch the regulator for a switching reg or a 7805. And don’t clip the heatsink
A switching regulator perhaps if you have the board space to lay it out properly. The 7805 however is a bad suggestion as it has the same power issues of the LM2937 but is not low dropout. This means you need nearly a 3V differential between supply and load to guarantee the performance of a 7805 over its rated output current range. A 7805 may work off of a 9V battery for awhile but it will start to drop out of regulation a long time before the LM2937 does.
I agree, the 7805 is a bad idea. The 2937 is a great regulator for this purpose. It requires only .5vdc over the regulated output to operate correctly. I alway power my robots from one battery and never have issues. For example a 6vdc battery pack will work reliably to power the servos AND the electronics even when the voltage drops down to 1.1vdc per cell.
The problem is, was, and will always be, people using inadiquate power supplies, or power delivery systems. This includes old crappy batteries, cheesy plastic battery holders, too small batteries, too small wires, wires twisted and taped, under current or analog wall packs, etc. Funny thing is we sell heavy duty wiring harnesses, battery packs, and a fairly decent wall pack at realistic prices. 
The 7805 has a 40V limit though if that is what you are looking for.
There is more to consider than just input voltage though. Even if the load is only 0.3 amperes (300mA) with a 12V input the power dissipated by the regulator is over 2W, which without a heatsink of some sort WILL shut a linear regulator in a TO-220 package (or a TO-263 standing vertical) down hard.
If you are looking to support a 40V input with no significant heatsink you need to look at a high frequency switching buck regulator. Linear Tech., National Semi., and several other common manufacturers have built up some serious product lines to meet this need in recent years. At low current levels some devices operate in discontinuous mode and can operate down to low-dropout input voltage levels. The penalty of course is cost and board space.
