Must a have 7,2V batt. on the hexcrawler? This moment i have a 4-pack 1,5V batt. = 6V. Is 6V enough? The legs·must to go walking after the thuning. The Home position is posible, thats the only movement a see on this moment. Thanks
Gerard
You'll need the 7.2v battery pack for the servos and you'll need to use a 9v or the 4 AA baateries to the BASIC Stamp in order for this to work properly.
What you describe is typical of sharing a power supply between servos and motors. If you observe a continuous "homing" of the servos accompanied with a flash of the green LED on the BOE, your power supply is probably drawn below the BASIC Stamp's brownout-reset. One way to test this theory is to seperate the power supplies between the Stamp and the servos.
You can use 6V on the servos, but you need lots of current. That's why we recommend the 7.2V R/C car batteries - they deliver lots of power.
Note a common error people make is to separate the grounds. The grounds of all batteries, and the Servos, AND the BS2, MUST be connected to each other. The Positive terminals MUST be separate, but the Grounds MUST be connected. The Servo uses its ground as the reference for the BS2 PULSOUT signal. If the grounds aren't connected, there's no telling what the PULSOUT signal looks like to the Servo.
I echo what is being said based on my experience so far with the Hexcrawler.
Make sure you tie all grounds..I didn't make that mistake, but read the caution enough times to heed it..basic circuit design tells you it is necessary.
Keep that 7.2V, 3000 mAh battery all alone for the servos...it pays off...and don't think for a minute 3000 mAh is too much.
I used separate 9V batteries, 3 of them, for the BS2, and the two SSCs (I have an "older" Crawler..). When I put the R/C portion on, I am going to clean up the battery/power supply side of things, and make it a lot simpler.
Also, as I learned by trashing a servo on the S3 head as I was testing, you need to be very careful when you disconnect power. It seems disconnecting power to the servos FIRST, then the BS2 and SSCs prevents stupid mistakes.
Thank to jou all. I have buy a 7,2 3000mAh battery and that are the soution for all my problems. A job are the tuning of the servos for the legs. But all working now.
Just a question about battery lasting time. I own a Quadcrwler, plus a S3 head, that is,·there are·10 HS322HD servos in my quad.
I use a 3000mAh 7.2V RC battery only for servos, and·one 9V only for the BOE.
The 9V battery lasts for a reasonable time but the 3000mAh runs out in less than 15 minutes.
And believe me, I don't do much work with the legs. For example, I can being testing the robot on a bench (no contact with ground) and it takes between 10 and 15 minutes to be dead again.
I use two similar battery packs for replacements, so battery·does not seem to·be faulty.
As for the charge I·use a quick charger. It charges the 3000mAh in about 80 minutes. Perhaps too fast ?
The life of your battery also depends on HOW you charge it as well.·At CrustCrawler, we use both 3000 and 3300 series niMH batteries. On a hexcrawler, these batteries will last 30 - 40 minutes of continuous·use with heavy payloads. What I have found is that you need to ensure 2 things with your batteries:
1. Ensure that you do not "quick charge" them as this is an option on almost all chargers. Make sure you drain any current that is left·(using the charger) and then "trickle" charge them.·Trickle charging will take about 1 -2 hrs.·Quick charging these batteries will only take 15 minutes or so...I big difference in the life of the battery.
2. Place a 1,000 uf· - 1500uf capacitor·across the leads of the battery. This trick will help to stabalize battery output power and avoid excess current·spikes from draining the battery before its time.
I wonder if you'd care to follow up more on the pre-conditioning before slow charging NiMH batteries, in draining them "using the charger". I'm fairly new to using NiMH batteries, but we have a long history of using NiCd batteries of standard and high amperage capacities. I'm basically in learning made with NiMH batteries at the moment.
From what I'd read so far, NiMH and NiCd's can be treated pretty much the same including using dual chemistry battery chargers (NiMh or NiCd), and the same caveats about not overcharging them, the benefits of slow vs. fast charging, avoiding high temperatures by using proper ventilation during charging, and avoiding possible reverse polarity situations (not draining the battery to zero volts and beyond) all seemed to apply.
In the past I've seen NiCd chargers used in R/C applications which had a built-in battery drain feature, but honestly never paid too much attention to them, nor have we ever used them. Ours is a robotic but non R/C application where the limit of battery use is determined by a pre-determined low voltage cut-off: (1.25 VDC > DC cut-off limit > .50 VDC) when viewed on a per cell basis.
From a practical as opposed to a technical point of view, would you feel that NiMH batteries under such conditions need be drained as well in this sort of application, and if so, to what point? We never bothered doing that with the NiCd batteries and never experienced any real problems, but the NiHM batteries we've been testing seem to be giving us a much short per-charge life than we would expect vs. a similar NiCd set of batteries (given the same total mAH capacity).
Thanks for your thoughts and the benefit of your experience.
We use only NIMH batteries for our robotics. In doing so we have found that not all brands act the same. I have a few that only last about the short length of time·that you describe. Other packs·last 2 -3 times longer. My feeling is that some of them are not constructed and/or the quality of materials /chemistry of the batteries is not up to standard or defective.·Trickle charging them definately makes a difference in the longetivity of the battery pack compared to a quick charge cycle. Also, having that capacitor across the leads of the battery will increase it's life noticably.
There is no specification for NiMH batteries to be drained for charging as they do not gain a memory like nicads. we are currently using the 3300 series NiMh batteries from Maxx products and they are working very well. This may be a coincidence but I have found that if I "condition" a new NiMh battery through 2 cycles of a trickle charge on a good digital charger I can obtain·good performance from the battery throughout its life cycle.
As mentioned earlier in the forum, make sure that the·leg(s) do not have a #8 screw(s) that has been over-tightened.
Comments
So insure that when you uppload the walking programs, that the Baud speed om the PC maches the speed on the BS.
Good·luck
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This is a student project
You'll need the 7.2v battery pack for the servos and you'll need to use a 9v or the 4 AA baateries to the BASIC Stamp in order for this to work properly.
Dave
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Dave Andreae
Tech Support
dandreae@parallax.com
www.parallax.com
·
What you describe is typical of sharing a power supply between servos and motors. If you observe a continuous "homing" of the servos accompanied with a flash of the green LED on the BOE, your power supply is probably drawn below the BASIC Stamp's brownout-reset. One way to test this theory is to seperate the power supplies between the Stamp and the servos.
You can use 6V on the servos, but you need lots of current. That's why we recommend the 7.2V R/C car batteries - they deliver lots of power.
Ken
Make sure you tie all grounds..I didn't make that mistake, but read the caution enough times to heed it..basic circuit design tells you it is necessary.
Keep that 7.2V, 3000 mAh battery all alone for the servos...it pays off...and don't think for a minute 3000 mAh is too much.
I used separate 9V batteries, 3 of them, for the BS2, and the two SSCs (I have an "older" Crawler..). When I put the R/C portion on, I am going to clean up the battery/power supply side of things, and make it a lot simpler.
Also, as I learned by trashing a servo on the S3 head as I was testing, you need to be very careful when you disconnect power. It seems disconnecting power to the servos FIRST, then the BS2 and SSCs prevents stupid mistakes.
Thanks Gerard Meyer
I use a 3000mAh 7.2V RC battery only for servos, and·one 9V only for the BOE.
The 9V battery lasts for a reasonable time but the 3000mAh runs out in less than 15 minutes.
And believe me, I don't do much work with the legs. For example, I can being testing the robot on a bench (no contact with ground) and it takes between 10 and 15 minutes to be dead again.
I use two similar battery packs for replacements, so battery·does not seem to·be faulty.
As for the charge I·use a quick charger. It charges the 3000mAh in about 80 minutes. Perhaps too fast ?
Anyone has a similar experience ?
My battery are low after about 30 min.
by Gerard
1. Ensure that you do not "quick charge" them as this is an option on almost all chargers. Make sure you drain any current that is left·(using the charger) and then "trickle" charge them.·Trickle charging will take about 1 -2 hrs.·Quick charging these batteries will only take 15 minutes or so...I big difference in the life of the battery.
2. Place a 1,000 uf· - 1500uf capacitor·across the leads of the battery. This trick will help to stabalize battery output power and avoid excess current·spikes from draining the battery before its time.
Alex
CrustCrawler Inc.
I wonder if you'd care to follow up more on the pre-conditioning before slow charging NiMH batteries, in draining them "using the charger". I'm fairly new to using NiMH batteries, but we have a long history of using NiCd batteries of standard and high amperage capacities. I'm basically in learning made with NiMH batteries at the moment.
From what I'd read so far, NiMH and NiCd's can be treated pretty much the same including using dual chemistry battery chargers (NiMh or NiCd), and the same caveats about not overcharging them, the benefits of slow vs. fast charging, avoiding high temperatures by using proper ventilation during charging, and avoiding possible reverse polarity situations (not draining the battery to zero volts and beyond) all seemed to apply.
In the past I've seen NiCd chargers used in R/C applications which had a built-in battery drain feature, but honestly never paid too much attention to them, nor have we ever used them. Ours is a robotic but non R/C application where the limit of battery use is determined by a pre-determined low voltage cut-off: (1.25 VDC > DC cut-off limit > .50 VDC) when viewed on a per cell basis.
From a practical as opposed to a technical point of view, would you feel that NiMH batteries under such conditions need be drained as well in this sort of application, and if so, to what point? We never bothered doing that with the NiCd batteries and never experienced any real problems, but the NiHM batteries we've been testing seem to be giving us a much short per-charge life than we would expect vs. a similar NiCd set of batteries (given the same total mAH capacity).
Thanks for your thoughts and the benefit of your experience.
Regards,
Bruce Bates
There is no specification for NiMH batteries to be drained for charging as they do not gain a memory like nicads. we are currently using the 3300 series NiMh batteries from Maxx products and they are working very well. This may be a coincidence but I have found that if I "condition" a new NiMh battery through 2 cycles of a trickle charge on a good digital charger I can obtain·good performance from the battery throughout its life cycle.
As mentioned earlier in the forum, make sure that the·leg(s) do not have a #8 screw(s) that has been over-tightened.
Alex