Mjv4721
Resolved by Rich!
Hi peeps,
I'm new to the Ez-Robot community. I recently put in an order for the JD Revolution bot, excited about its arrival, even though it's in stage 2
I've been reading up about LiPo batteries and I am now sufficiently perplexed by the numerous complications surrounding all things LiPo...
From what I know, the JD kit includes a 1300mAh 7.4VDC LiPo battery (charger incl), but to better my understanding of what this means (pardon my ignorance if I ask stupid questions, but I am still new to a few of these things) this would mean that:
7.4 volt battery = 2 cells x 3.7 volts (2S)
Essentially, the battery pack is a 2-series LiPo battery pack. Subsequently at 100% charge, this battery pack would output roughly 8.4V?
From what I've read, LiPo batteries don't like being discharged past 80% of their capacity for numerous reasons, so I have the following question:
I'm assuming the EZ-B v4 does not cater for LiPo batteries going below 80% of their capacity as the the use of battery is not known upfront and for a number of other reasons. (also assuming this can be done easily as an extension by the end-user).
What's the best way to measure the voltage coming from the battery with regards to the EZ-B? For instance, the voltage reading detected by the EZ-B is 7.6, call an algorithm to move to the charging station or move to a safe zone and shutdown so as to limit the damage to the batteries?
I just need a basic idea of what needs to be done, I'll try and figure out the details as that's the fun part of the project
Just to give some context as to my experience level - I've been programming in C/C++/C#/Java for about 10 - 12 year now, but my experience with electronics is minimal. I know the bare minimum.
Thanks in advance!
Kind regards,
Marius
In essence though, what I am looking for then is a low battery indicator I suppose... What can I read up about to get an idea around implementation?
I want to implement a low battery indicator that gives the robot (taking into consideration the average battery current consumption rate) sufficient time to reach the charging station/safe zone.
So I think I would possibly need: A way to measure the remaining battery charge (possibly get this from EZ-B directly without additional components?)
A second ADC port can monitor the first cell of the battery with no additional circuit since it's fully charged voltage is 4.2v.
The same script, or a different one if preferred can be used to calculate cell 2's voltage.
Have a look at my LiPo Monitor tutorial for more.
This gives me a good start and an idea of what I can do.
I just had a read on what Zener diodes are and how they work. Your circuit makes more sense now.
Have a few questions though if you don't mind answering (with reference to the second diagram in your tutorial):
1) R1 in your diagram I take it is used to drop the Vin to the required output voltage?
2) R2/R3 I'm not too sure what they are for though?
3) Would an additional fuse in the circuit be overkill to protect against over-current given that the resistance chosen is sufficient to account for the power dissipation? (My apologies if this doesn't make sense, did a crash course in Zener diodes today)
Also, you mentioned in the tutorial you were considering looking at a shut-off circuit for low voltage situations, did you ever get around to finishing such a circuit?
I'd be interested in having a look at how you went about designing that as well.
The diode is there to protect against over voltage (however on my physical circuits I made I don't use the diode since I didn't have one).
Google for Voltage Dividers and you'll find the same schematic/circuits all over the internet with great write ups and explanations.
Thanks Robot-Doc, just enjoy learning how most of these components work even though I will end up using bits and bobs to build components instead of doing it myself.
Cool stuff
The EZ-B v4 also has a temperature sensor built into the CPU - so the cpu core can be monitored for thermal shutdown
I would like to handle the low-battery events as mentioned to either move to a charging station or shutdown completely.
On a side note, will the ez-openbot project be maintained to for the EZ-B v4 specification?
Thanks for the cool product, looks amazing thus far. Can't wait to get my hands on my preorder.
So many uses. return to charging station, graceful shut-down of embedded computer, send an alert (email/twitter, etc...).
Alan
TBH I've really been exploring more of the physical engineering. I'm kind of weak there I feel. I've built a few bots but none of them have lasted long enough to really explore all that the EZ has to offer.
I like using the keyboard control for movement and have made a few scripts for a pan and tilt keyboard control. One with standard servos and recently, for my Roli, one that uses modified servos. I had them and didn't want them to go unused. Since I want to pan and tilt at a slower pace anyway using them doesn't seem to be an issue. And I had the ping sensor working on Fifah. But that's been about it.
There are two others I had design issues and put on the burner. Roli is replacing one of them so, having Roli to build off of is very exciting for me and any goodies you want to throw into the software are just more toys to play with. Very excited to hear about the new EZ Bit gyro and others showing up in the store soon. I can't afford to buy anything right now but, I like window shopping.
Sorry to rant but I'm getting excited now.