Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Private Reid on April 07, 2008, 05:53:51 AM
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I'm a little confused see.
Is it only Atmel microcontroller product that you have to use servos to dive your wheels (without using a H bridge)
Because I have seen other robots that don't use servos...infact almost all of them do.
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You do not have to use servos with the Atmel chips. And you do not have to use motors with most of the other microcontrollers. If you see a robot that is using motors instead of servos it means they have either an H-bridge or an Electronic Speed Controller someplace in the circuitry driving the motor. I don't know of any hobby level (or otherwise) microcontroller that can directly handle the amperage required to drive a motor directly.
Servos are just easier because you do not need an H-bridge or ESC and they come with built in gearing.
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Servos are good for small size robots (under 1 foot cubed) because of internal gearing and internal motor controll circuitry. Servos use regular DC motors. The advantage is simplicity in connecting it to the microcontroller (only one pin) and logic controll (simple PWM signal).
DC motors will come in handy for a bigger robot. But you need to build (or buy) a motor controller and a gear box. Most of the DC motors used in robotics are allready geared. Even so, may robot builders add an extra gear reduction stage mostly because it is better to mount the wheels on a separate axle (because of weight being better supported by ballbearings instead of just the gearbox bushings). But there are also advantages when using DC motors. Higher speed, higher torque, regenerative system, better speed range, even the use of a single pin from the microcontroller is possible. Also they use PWM controll signal. For small and medium size motors there are simple to use integrated circuits (H-bridges).
All in all, the choice of using servos or geared DC motors for your robot is yours. It all depends on what you want the robot to do. If you want a simple to use solution, use servos. There are faster servos or bigger wheels if you need just a little more speed. If you want higher torque or speed with smaller wheels, use DC motors. If you want a legged robot, use servos. If you want a ballancing robot, use DC geared motors (they have a greater speed range, verry usefull for a ballancing robot).
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well you can use anything you want as long as you know that you can control it , but for you i would reccomend go for a servo as they easier to control and light weight but learn up the servo modification for full 360 degree first ;)
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Thanks.
well you can use anything you want as long as you know that you can control it , but for you i would reccomend go for a servo as they easier to control and light weight but learn up the servo modification for full 360 degree first ;)
exept servos are $$$
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yup both dont think motors will be cheap, a normal 200 rpm geared motor will be 6$ each and also u need the h -bridge chip like l293d or l298
cost of l293d will be $3 and l298 will be around $6
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exept servos are $$$
Servos are not expensive!!! Get the hs-311 for 9 bucks! Much easier then motors.
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exept servos are $$$
Servos are not expensive!!! Get the hs-311 for 9 bucks! Much easier then motors.
Before I found out about SOR I thought that robot parts would go at like 90$ at its cheapest and that it could cost you somewhere around 600$ to make a basic robot. I think that many parts are extremely cheap, those servos included.
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exept servos are $$$
Servos are not expensive!!! Get the hs-311 for 9 bucks! Much easier then motors.
What the hell !!!!!
$9 !!! :o
In Australia there like frigin $60 for 4 !!!!
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If anyone is willing to post me 2, hs-311...
;D :D ;D
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What the hell !!!!!
$9 !!! :o
In Australia there like frigin $60 for 4 !!!!
In Romania they are about $19 a piece...
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i guess we cant do anything abt it , we just have to adjust accordingly
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i guess we cant do anything abt it , we just have to adjust accordingly
Hmmm
Like my $50 robot is now ONE HUNDRED AND FIFTY DOLLARS !!! :(
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yea admin should of said what it was going to cost on average for different countries,cos mine has cost a fair bit too,its $45 just for the cable to program my robot(but i have to make it as a kit :().so in aus the $50 robot is more like the $500 robot,lol maybe i exagerate a little ;D hey u americans how much does it cost for 1 hitec hs-322 servo,cos it cost me $18,god damn price difference lol ;D
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yea admin should of said what it was going to cost on average for different countries,cos mine has cost a fair bit too,its $45 just for the cable to program my robot(but i have to make it as a kit :().so in aus the $50 robot is more like the $500 robot,lol maybe i exagerate a little ;D hey u americans how much does it cost for 1 hitec hs-322 servo,cos it cost me $18,god damn price difference lol ;D
soooooooooooo true
so in aus the $50 robot is more like the $500 robot
NOT AN EXADURATION
hey u americans how much does it cost for 1 hitec hs-322 servo,cos it cost me $18,god damn price difference lol
im intrested
but i need to know how much for a hs 311 servo
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I feel sorry for you people in australlia. Here are the hs-311 servos http://www.servocity.com/html/hs-311_standard.html. Servo City ships anywhere.
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Shame its out of stock ;D
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well the cost is that much coz its a local company for america and its an international company for the rest of us , i cant imagine what a microcontroller will cost or worse a development board
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yea but that $18 dollars was from a local company or is it cos the company imported it from america
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yea but that $18 dollars was from a local company or is it cos the company imported it from america
Its probably because they dont have any competeition price wise and so they can dictate what price you pay.
It sounds like a business opportunity for some australians on the site to set up a competetive priced robot parts store, but check first about import taxation because this might be part of the reason for the expense.
In england, theres only 1 importer of hitec servos(hs-311) and they are £4.11 ($8.08) to buy from at trade price and they must be bought in quantities exceeding $500 ($493), so businesses that sell them for like $9 arent making very much profit on them at all.
Here is the link for the hitec distributor in australia http://oos.modelengines.com.au/command/servlet/Command?command=display_item_pub&pkey=meng&f_id=1&itemid=HTHS-311BULK (http://oos.modelengines.com.au/command/servlet/Command?command=display_item_pub&pkey=meng&f_id=1&itemid=HTHS-311BULK)
the hs3-11 servos are (AUS$8.10 US$7.51) each, but you might have to make a minimum order to buy from them. (the distributor is where shops buy from. The shops then add a bit onto the price for their own profit so shops marking them up to $18 are just being greedy)
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thats a big problem , why dont countries except america have good supplies of servos and microcontrollers?? and cheap too??
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Volume sales. Or the volume of sales... something like that.
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well if u ask for volume , then ill say all countries have a fair share of robotists , so why so much problem in getting all the materials in countries apart from USA
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Shipping, customs, handling... it all adds to the price. If there is a small quantity, the price will be high. Also the profit of the seller is large at first, then it goes down after a few times, because of discounts from supplyer, shipping company, (probably not from customs...) and the quicker money return from selling the merchandise. Large quantities will get lower price per piece, but a higher price per lot. A big lot will probably sell over a long time, so there is money that is blocked in the stocked merchandise. All this counts. I have looked in making a store in Romania, but the slow return for the invested money made me change my mind.
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this isnt fair u know, i mean sometimes what u need is things that are readily available and not ordering in the internet coz they take many days to ship and reach here , so i hope that shopkeepers soon start importing these servos and other robotics materials so that ppl can buy them easily and dont have to follow useless rules and regulations and wait even more after ordering in the net
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If you look at the link above, they are the australian importers/distributors. They always carry a stock for the retailers to buy from(so the price you see is what you pay, theyve already done the customs and import thing). Even you could buy from them if you were willing to buy enough to make it worth their while, if you ever get a few hundred dollars spare, buy some and sell the reserve stock yourself, ive started doing something similar but only electronic components for now(you can get most at over 50% discount when bulk buying!)
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well, im in singapore.
over here, hitec HS-311 servos are 24 bucks. the exchange rate between US and singapore is 1.4
the shops here do not have loads of the products too, i only had a choice of ONE AVR programmer and TWO controllers...
that alone burnt a hole in my pocket..
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even a country like singapore has such problems ... seeesh this is kinda global , something has to be done
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Most suppliers, like DigiKey say, will ship anyhwere but you need to spend $200 to get free shipping otherwise the shipping is more than the cost of the goods. Anyone want to create a buying portal that the Auzzie members, say, can all order via and have stuff shipped to a central place in Oz and then pay local postage to their own home!!!
Hhmmm - or could SoR get group discounts for all of its members
Could be a business opportunity?
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it not only abt aussies , its kinda global all of us need cheap and easily available equipments in our countries which we dont have now, i think ppl are not yet looking at the business side of the availibility, there are many robotists who want to buy such things cheap but end of ordering from the net where they have to pay double the amnt of the equipment just for shipping which is quite adhoc .so if local vendors get these products, they will earn a good profit and robotisits will get their equipments very cheap..
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There has to be a demand on the market first, only then the local vendors will get the products. Two years ago when I came back in Romania from the states, the were just a handfull of people interested about robotics. Now, there are contests in the university and many students start to be interested in the hobby. And slowly, some stores start to get products, but from Europe (more expensive than USA or directly from asian manufacturers). The orders take weeks to be delivered and we pay double the price for the parts (and shipping).
I am soon going to be in Canada and I allready saw that the prices there are a little higher than those in the States. Probably because of customs. Wen Admin will send me an Axon, I will have to pay international shipping and customs. So, I will pay about 10% more than the americans. I guess this is the same for any other country in the world.
Ehh, I still have another 3 years untill I'll get back to the States...
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This is one of the things local robotics clubs can be invaluable for. Not only to drive up demand for a product such as good servos in the local market (thus reducing price) but also for bulk ordering to offset the cost of shipping. If you pay one servo at $9.00 from the internet and pay $35 in shipping/import costs, you just bought a $44.00 servo. But if a group of say 6 hobbyists each pay $9.00 for a servo plus the $35.00 shipping/import costs they each just bought $15.00 servos. A bit more reasonable of a price... The more the import and shipping costs can be deferred across multiple products, the less you are paying per product.
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Sorry guys, I don't control the international market prices :P
As suggested before, try to find local websites selling your parts. No crazy shipping that way.
And its not hard to start an internet company - if you think the demand in your country is high, start buying and selling!
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Can use dirt cheap Futaba S3003 as well, they cost 10 euros and 180°(alomost) range.