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Electronics / How to connect a servo with microcontroller p.s I am a beginner :P
« Last post by MBJ on January 17, 2015, 05:55:16 PM »
My robotics kit is not here yet but
if I have a microcontroller and I have servos, batteries etc.
How should I connect them? I mean how would I know that this is the right way to connect them or how would I know the difference in the input and output ports.
and is it possible that I bought a microcontroller and a servo from different places and the servo is unable to connect because its pin (or wire or lead) is of different kind and the port on the microcontroller is of different kind? is it possible?

Thank you!!  :)
Electronics / Re: Electric bicycle
« Last post by newbie_teach on January 17, 2015, 12:12:10 PM »
Thanks a lot for you reply,Sir. Any of these high power motors give a lot of rpm for example the one you showed me
http://www.ebay.com/itm/ELECTRIC-SCOOTER-BIKE-MOTOR-ENGINE-24-VOLT-250W-CURRIE-M-ST08-/361021196585?_trksid=p2054897.l4275 This one gives 2650Rpm on the shaft, that is a lot of speed(right?). I am a pretty heavy person, according to my . knowledge I would require more torque(correct me if i am wrong).To mechanically swap rpm and torque gears come into picture, what gear ratio will I have to use(sorry to be complete headache).I am trying to learn about gears as much as I can.A brief explanation though will be very helpful for me.
Electronics / Help with transmitter/receiver setup
« Last post by Cycloned on January 16, 2015, 08:41:16 PM »
I have a FS CT6 tx/rx and I'm having issues. Basically I want to use this for robotics, and connect it like shown in the SoR beginner robotics tutorial video. When I move 1 joystick upward, both servos should go forward and when I move it downward both servos should go back. However, when I tried this, both motors started rotating without me giving any input to the tx.

I have connected 1 servo to Channel 1 and the other to Channel 2. In the configuration software, I set the left joystick to make Channel 1&2 to go forward with max speed when the joystick is pushed upward, and vice versa for when it is pressed downwards. However, at the neutral position, 1 servo is rotates at normal speed and the other is rotating at a slow speed. I tried to make it stop by moving the trims but it hasn't worked. I found this very odd because in the configuration software, it showed that at neutral position neither servo was being turned on.

How can I accomplish this?
Electronics / Re: Help Choosing A Battery
« Last post by Tr4nz1uc3nt on January 16, 2015, 04:08:41 PM »
Thanks for the help! I'll definitely take a look at those. I wasn't aware of the danger of that kind of battery, but if I get one I'll be sure to treat it carefully.

Much appreciated,
         Quinton Shipps
Electronics / Re: Help Choosing A Battery
« Last post by Schlayer on January 16, 2015, 09:01:14 AM »
The data sheet for that specific servo says it should definitely not be run at 9V; it is rated for 4.8-7.2V.  http://www.electronicoscaldas.com/datasheet/MG995_Tower-Pro.pdf
You will definitely not want a battery with a voltage over 7.2V, so I would recommend a 6.4V LiFePo4 pack (google Lithium Iron Phosphate). Ordinarily I'd stray from something like that, but only due to the dangers associated with Lithium battery packs. However, for running 12 servos and a micro controller, you're gonna need the energy density that LiPo can provide. Now we just have to figure out the current you'll need.
The data sheet doesn't specify what max current the Servos can take, but it does say that they are meant to run off of a variety of R/C receivers, all of which I know provide around 5V at usually 2A or less. However, they are usually meant to power multiple servos simultaneously, so I'm gonna take a guess and say each one needs a ballpark of 0.5 A. That means you need to supply up to maybe 6A at one time to power 12 of them. This is probably a bit low, but you will also rarely need all 12 moving at once at full speed, so it's probably a fair estimate.

On BatterySpace, the cheapest/smallest battery that could suit your needs is this: http://www.batteryspace.com/LiFePO4-18650-Battery-6.4V-1200mAh-Flat-7.2Wh-10A-rate.aspx
However, this would provide an absolutely pitiful run time. Assuming you use an average of 4A continuous current, not adjusted for inefficiency (which, let's face it, there will be a lot of with 12 of these guys either idling or running), you will have 1.2Ah / 4A * 60min/h = 18 minutes run time. You're getting just over a minute/$ on this battery. Let's see what else might work...

This battery has twice the storage capacity and is only $35, so it will provide 36 minutes of run time with the above estimate. http://www.batteryspace.com/lifepo418650battery64v2400mahsquare144wh14aratewithpcbandpolyswitch.aspx

This battery seems like the best value: http://www.batteryspace.com/custom-lifepo4-26650-battery-6-4v-13-2ah-flat-84wh-16a-rate-7-9.aspx At 13.2Ah it dwarfs the others, though it costs over twice as much as the last mentioned at $74.50, and as a large pack it'll probably be cumbersome to your robot and your shipping costs. I'd expect it would cost closer to $87 shipped. However, the run time you would be estimated to get is... wait for it.. 198 minutes! Even after losses and powering many things besides just the servos, you'll likely get well over 2 full hours of use out of this thing on one charge. Note well: you should never actually get 198 minutes from this guy without discharging it to a dangerous level, but 2 hours is very realistic and likely repeatable.

I hope this helps you somewhat. Just keep in mind that without the proper charging equipment and maintenance, you can have a lot of problems with Lithium batteries, especially LiPos. My brother learned this the hard way when he had a LiPo charger malfunction, causing the battery to overcharge and eventually explode and burn a hole in his carpet, which fortunately was as far as it got before firefighters dealt with it. This is a very uncommon occurrence, but nevertheless, I cannot emphasize it enough:
Never leave a Lithium Polymer battery unattended while charging!
There are very visible signs such as inflation of the cells and excessive heating that can give away a potential fire hazard before a disaster occurs. Also, in the event that your battery does fail, instructions indicate that you should never leave it unattended, and if you have, you will not have grounds for insurance to pay for the damages. I highly recommend you get a smart battery charger recommended by BatterySpace such as this one: http://www.batteryspace.com/smartfastcharger12aforany64v2cells76vcut-offlifepo4batterypack.aspx
It's not even that expensive, and it is well worth it.
I hope this helps!
Electronics / Re: Autonomous Ground Vehicle
« Last post by yxsilentxy on January 16, 2015, 02:31:37 AM »
Size is dependent on the group and how crazy we want it to be. The robot is supposed to follow GPS coordinates around a parking lot, so from point a to point b. There are 4 yellow giant containers that mark the inside boundary that we're not allowed to go into. There is a slalom of red barrels, a green hoop, and a blue ramp that we have to maneuver. We're given $1000 and the project deadline is June 22, 2015. We have a group of 5 that are split into hardware and software, me being on the middle, so I have to deal with research of hardware and software. Most likely programming in C (Arduino).
Electronics / Help Choosing A Battery
« Last post by Tr4nz1uc3nt on January 15, 2015, 10:26:38 PM »
Hello, I am going to build a quadruped walking robot with 12 MG995 metal gear servos, but I honestly have no clue what kind of battery to use to power them. A 9 volt battery will power one fine, but it does not have enough current to power all 12 at once. I am not new to making robots, but I have never built one from scratch like this. Any help is greatly appreciated!

Thanks in advance,
     Quinton Shipps
Software / Need help for Voice recognition car
« Last post by APJ1234 on January 15, 2015, 05:34:24 PM »
Hey guys can somebody able to help me through my whole project?
Electronics / Help regarding which programmer to choose for $50 robot
« Last post by kalpeshprithyani on January 15, 2015, 03:48:15 PM »
I was searching for a good AVR programmer to programme my $50 robot but couldn't find one.
However I came across this thing, before ordering it I just wanted to confirm from you people that whether this will work or not?

USBasp USBISP AVR Programmer ATmega8 ATmega128

With "work" I mean with software ponyprog?

If anything is better than this please do suggest.
I am a beginner, I am from India (if anyone is from India, he must be knowing the pain of arranging parts for the robot. :'( ), I can't consider shipping an option from sites digikey or sparkfun because it costs like $50 just for the shipping purpose, which is not possible for me right now. And also because I am a beginner the searching for the right product becomes even more difficult.
So please do help.
Misc / Re: anyone from india
« Last post by kalpeshprithyani on January 15, 2015, 02:39:57 PM »
I am from India, check this site robomart.com.
It do contains some of the robotics stuff and it is also cheap.
lack of availability is the only problem.
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