Where can I buy gyros/yawrate sensors that fit with the requirments (price wise) and can interface w/ the robot computer w/o any custom circuitboards or anything? Can i use the Analog Devices ADXR150EB ? I’m not sure if it works with the robot controller and outputs the same stuff…
http://www.drrobot.com/products_wirobot_list.asp?categoryID=7 is a good source… the ADXR150 outputs a 40KHz samplerate ‘analouge’ value ( do a search on this there are hundrads of posts ) and can be read by the RC ana_in’s
you could use the Analog Devices ADXRS150EB which has a +/- 150° per second rate, or the Analog Devices ADXRS300EB which is +/- 300° per second
we are using the 150 on our bot - you connect +5 V and Gnd to a couple pins I think there are 2 +5V pins - and the signal that is produced if perfect for the analog inputs to the Robot controllers - roughly 0 to 5 volts
I got a pair from Avent electronics for $50 each - I dont know if future or digikey has them in stock - their prices were higher.
search on ADXRS150EB here on CD - you will find several threads discussing how to use them.
I could not find any Gyros on the Dr. Robot page that you gave me…maybe i don’t geet something… can you give me the web address for avent electronics if i search i just get loads of garbage…
btw the gyros from 2003 or 2002 are definitely overpriced right?
oh gosh- Ive been so brain dead lately!
I spelled it wrong in my post - its Avnet
sorry about that
edit: this is the electronics part page - but they show none in stock now
you might try calling them - they may stock them as samples since they are evaluation boards
Aha…thanks…do you know of anyother places where i can be able to get them? anyone ? Thank You
if you cant find any from the distributors or catalogs, you might start a new thread specifically asking if anyone has a extra ADXRS150EB that they could spare?
I got two and would hate to give my only spare away, since its vital to the operation of our robot
but some teams might have purchased several and be willing to give up one.
but I would start a new thread to ask - not everyone reads everythread on CD all the way to the last post.
Remember that even if you get the part from a different source, you must count the digikey/future active/newark price when doing your BOM.
edit: nevermind, see below
That’s what I thought as well, but the FIRST Q&A says differently:
Q: We heard that a single gyro evaluation board (ADXRS300EB) at Future-Active costs $100.50, but if several are bought, the price is about $97.00. Also the device is available at Analog Devices for $50.00. Is it legal to use this part?
A: You may use this part, and the lower price from Analog Devices is OK for costing purposes.
oops, I misread that message on Q/A. I had though it said the lower price from future active.
digikey lists them for $75 - so they are technically not over the $100 limit for a single item rule - thats the price I put on our BOM, even though we got em for $50
its like, if I give you one for free, you still have to put down its ‘normal’ value.
Should I buy the one with the PC board (EB) or ABG which it just says is a GYRO
Order the EB (evaluation board). It comes in a 20 pin mount that’ll fit right into a regular printed circuit board.
The other is impossible to solder without very specialized equipment.
The ball grid array is a MAJOR pain to work with. It took a very skilled electrical tech in our building 4 hours to wire a single yaw sensor and another similar 2D accelerometer (ADXL202) with the circuit that comes build into the EB versions. The only reason we did it was to meet the $200 limit. Now that FIRST has made the limit $300 and has allowed us to use a $100 “EB” part while only accounting for a $50 “ball grid” part (see above), there is no way I would have had a team member spend that kind of time (the only benefit is that it “saves” $50 – not worth 4 hours of a persons time).
Bottom line: Buy the EB version and run.
This circuit board that it fits onto…where do i get it…do i have to make the circuit board or something like that???.. We don’t really have that capability…i mean i was hoping 3 wires… ground 5v and signal and i’d just put some crimps on
the gyro chip itself is a tiny little thing, about a 1/4 inch square, and its a ball grid array device (BGA) - instead of pins it has a matrix of solder balls on the bottom that melt down onto a grid of pads when assembled onto a printed circuit board
thats why we advised everyone to get the EB version - its the gyro chip already mounted on a small printed circuit board, the size of a 20 pin DIP package if Im not mistaken, and it already has decoupling and filter caps on it
you could mount it on some of the protoboard they gave us in the KOP - the stuff you used to make the beacons - cut a piece big enough to put mounting screws through with the EB device in the center - attach the three wires (I think you have to connect power to two pins)
and you will be ready to fasten it to you bot.
We put ours in a black plastice 1x2x4" project box from radio shack, just to protect it.
BTW - you need to mount the board/box solidly to your robot frame - it cant be just hanging loose, or even on tape -you want a solid mechanical connection to the frame so the sensor moves exactly the same as the frame moves.
Like Ken said, it isn’t difficult.
You’ll be attaching 5 wires total to the chip. Several of them combine, so you end up with three wires going to the RC.
pins 8 & 12 = Ground
pins 1 & 13 = +5v
pin 2 = signal