Li-ion Power Pack
Will the the Li-ion Power Pack work okay with the Activity Bot. I haven't done much looking yet, but I haven't found anything yet that says it will for sure either.
Anyone know for sure?
Power requirement for the Activity Bot is 7.5 VDC; as five 1.5 V AA batteries.
Output for the Li-ion Power Pack is Nominal 7.4 VDC; 8.2 VDC maximum - Should be okay, huh?
Anyone know for sure?
Power requirement for the Activity Bot is 7.5 VDC; as five 1.5 V AA batteries.
Output for the Li-ion Power Pack is Nominal 7.4 VDC; 8.2 VDC maximum - Should be okay, huh?
Comments
(famous last words)
But I can't say with any technical backing....just anecdotal evidence!
Sound like a good Father's Day gift!
I will post my findings too!
The activity board can take up to 9V for Vin so the Li-Ion pack's 8.4V (freshly charged) would be just right. I was about to say to make sure and set the servo power jumpers to 5V but apparently the high speed servos can handle 8V. I'm not sure if the servos can handle the Vin when using the Li-Ion pack or not (a good question to ask Parallax). If you use the servo set to 5V, I don't see how you'd have a problem using the Li-Ion pack with the ActivityBot.
Chris, Do you know if the high speed servos can be powered from Vin when using two Li-Ion cells? I'm guessing not.
I personally like running CR servos from a regulated source. The constant voltage makes the speed very consistent. I found it next to impossible to get a CR servo robot to perform a figure 8 without either encoders or a regulated voltage source.
I had assumed that these servos are the same as Parallax's standard analog servos with taller gearing, which would make the torque suffer. Is that the case?
Most other servos don't recommend 8V, as most servo specs quote 4.8V and 6V performance.
The ActivityBot was tested with the Li-ion battery pack and found to work fine. I have not heard of any reason why it shouldn't work, however I will contact our education department this morning and see if anything has changed. I thought we were compiling a compatibility list at one time. I will follow up today.
It is a PDF file you can open/download.
We've tested our original servos ("normal speed" version) extensively. They run fine until about 8.2 - 8.3 vdc. At that voltage there is an internal capacitor that will fail at that level - some do and some will go even a little higher (8.4-8.5vdc). ("magic smoke" time)
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That's when you're connecting the servos directly to the battery voltage. However, if you're running the servos off of a regulator (ie vdd from a board), everything is fine. In fact, that's the proper input voltage (7.5-8vdc) for the Boe's anyway.
If you do get smoke to come out of the hi-speed servos, please let me know at what voltage that happens...it'll save me time in finding out for myself
-MattG
At the top of page 2 on under "ActivityBot Riobot Kit" and across from "Li-Ion Pack/Charger" it says:
I know from experience many servos can't handle that much voltage. Apparently the high speed servos are also high voltage servos.
The High Speed Continuous Rotation servos like 7.5 VDC, and are spec'd for 6-8 VDC. Trying to power the ActivityBot's high-speed servos at 5V while using the encoders and abdrive will make it unhappy.
Does the 5V regulator not provide enough current for the high-speed servos and other 5V devices or do the servos not work well with only 5V?
Freshly charged Li-Ions are often a bit over 4.2V. Will the 8.4V (possibly more) be a problem for the high speed servos?
I don't have an ActivityBot but I have a set of high speed servos (and AB wheels) I've been meaning to add to my PropBOE-Bot. I've been powering the servos on my PropBOE-Bot with 5V but it sounds like I should be able to power the high speed servos with the Li-Ion Pack's Vin?
Ray
Thanks for the answers! Looks like I need to start saving up.
Don't fret none, Br'er Whit+. The Lord (or Matt & Ken) will provide all you needeth!