The manual is kind of confusing about the power inputs with VL, VS and the VL/VS link.
It says not to use the VL if the VS link is used.
So if i supply 5v into the VS with the VS/VL link, i can power everything from a 5v battery right?
I know obviously not to use both VL and Vs with the VL/VS link enabled.
Right now my VL is 8.4v right from the battery, my VS(unlinked) is 5v from a regulator.
But i’d much rather power everything with a single 5v battery. (i have a nice Li-Ion 5v battery here)
I’m not going to go experimenting with this, i definitely need you guys to answer this one.
A 5v battery will probably not work for VL as the built in voltage regulator on the board needs a voltage higher than 5v. I believe it needs at least 5.5v, which is why a 6V battery works fine.
I have never heard of a 5vdc battery, Li-Ion or anything else. The LiPo / LiIon cells are 3.7vdc each. So it’s either 3.7, 7.4, 11.1, 14.8 etc. There is no reason you can’t use a single regulator for the servos, powered right from the 8.4vdc battery. The current isn’t that great for the servos anyway. So the requirements wouldn’t be that demanding.
the 5v dc battery, is a bit more, nifty, than that.
It’s a 4.x volt battery that was originally inside a PSP Power Grip, an attachment for PSP’s that has an internal rechargeable li-ion battery.
It also has a bunch of regulator and safety circuits, the battery has it’s own tiny circuit board on it too.
The charger works in a way so, you can plug it in with a psp 2A wall charger, and it’ll both power the psp and charge the battery, once the battery is charged it’s just a pass through adapter. Meaning i can attach the battery to the robot, and if it dies, i can plug in the charger and continue using the robot while the battery is attached AND charging.
The power output of this pack is 5v, the same as the input of the PSP. (despite psp batteries actually being 3.6v)
So if possible to run the ENTIRE robot, motor controller, servos, BB2, all off my 5v(out) battery pack it would save me both space, time, and from having to use regulators as i run both 5v on my servos and my motors.
I don’t really want to use 2 batteries, though i can, i just want to know if the BB2 would be ok running with 5v in, and if so, how should i connect it up?
It says not to use VL when using the VS-VL jumper in the manual which i attacked, last sentence of #7. BotBoard manual.PDF (930 KB)
Right now, I am supplying 5VDC from a PC power supply (not a battery) into VS and everything is running. I was wondering why this worked since the onboard regulator is documented to require more than 5VDC to operate. Curiously, although against my expectations, it does work…
You use the VS-VL jumper right?
Also, are all your device jumpers set to VS or to 5V?
There really should be some clarification with the power inputs. Like what you can and can’t do.
The guys over at pololu mentioned the regulator can still put out 5v, with only 5.5v coming in.
But the VS line supports 4.8v
I double checked with a multi-meter, the 5v batteries output is exactly 5.38v fully charged.
Ah, well technically it’s a battery with regulator. Ok np. If you are sure it’s regulated, then you can inject the 5vdc into the board after the regulator. You may need to remove the regulator from the board to do this. Some LDO regulators do not like their output pin to be of a higher voltage than their input pin.
Ah, maybe not worded very well. But it’s meaning is simply when you want to power both servos and logic from one battery use the VS terminal not the VL terminal. It’s ground plane is more robust and the servos do draw more current than the logic side of the board.
5.38 is too much for TTL CMOS logic. I have seen regulators put out 5.1vdc and be ok, but this is almost 5.4vdc. Too much, unless your meter is off by that much.
The power terminals couldn’t be any simpler…
VS = 4-8vdc to 7.4vdc. Depending on the servos requirements / capability.
VL = 6vdc to 9vdc. The 9vdc limit is due to the regulator not having a heat sink.
Powering everything from a single battery is done all the time. You must be aware of the possibility that the micro WILL reset if the servos / motors draw too much current. This will always be a potential problem, and is not a defect in the product, just the way ohms law makes things act.
With a load current of 500 mA the minimum input to output voltage differential required for the output to remain in regulation is typically 0.5V (1V guaranteed maximum over the full operating temperature range).
So because we aren’t drawing near the 500mA max the 0.5vdc minimum is surely ok. I would be interested to know what the output of the regulator is with only 5.0vdc in. I’m guessing around 4.8vdc. Right on the fence of working or not. Lucky?
If your battery (which seems to have additional electronics) has a stable +5v output, then you should be able to connect it directly to a +5v point on the board as well as the servo power points. Be advised that you would need to check the output voltage when charging. I power my ssc-32 off of the +5v in a USB hub by tapping in at one of the +5v points on the board.
“The 9vdc limit is due to the regulator not having a heat sink.”
Can i use 9.6 or 10.8v IF i put a heatsink on it? I’d remove the regulator, solder on a large heatsink, facing the ideal angle to get air on it from my robots fan, Ya it has a fan too!
And then put the regulator back.
Also would it be a problem if i used a pot-regulated circuit? in place of the regulator?
I’d put header pins where the regulator is, then use something like this.
I can set the power with a pot, then once i have a 5v (+/- 0.1v) output i can attach it to the botboard and away i go!
With a hearty 3A i can power everything on my robot, from what ever power vs or vl that goes to that regulator.
That way i can use ANY of my batteries, as long as i adjust the pot first.
I’d remove the pot while adjusting it, as not to damage anything, hence the header pins.
In my case, the actual output of the PC power supply is 5.19 volts and is rated to 8A. The output of the SSC-32 regulator, measured at the + - header pins opposite the ABCD inputs, is a steady 5.0VDC
Lucky?
Thanks for the info, Jim. It’s exactly what I was curious about.
