I am sorry, but I was involved with FIRST two years ago, and had to take a year off last year because I started a new job…so this might NOT be a new item this year…
But is this CUSTOM board a new item? I am excited about it, ecen though I have not yet had a chance to see the ADDITIONAL HARDWARE list allowed on it.
What do you expect to do with it?
How about measure currentls of all motors to keep from popping breakers!
Can you do some signal conditioning on some of the sensors…to either take some of the labor off the stamp, or perhaps somehow monitor stimulus or feedback that might otherwise been difficult to do. (accelerometers maybe?)
Who knows, but even with such a simple game, my imagination is running at 100 miles a minute!
I am only 20% finished with the download of that huge PDF file, and I only wish I could get at it right now to see what the limits on design freedom might be.
(I am experiencing a sort of mental salivation over all this as I sit and wait for the download)
I think this could make for some very cool robots, and definitely some more powerful ones. Is anyone planning on doing a custom circuit board? What for? Replacement of the entire control system? I’ll post some ideas when I refine them a bit.
In the past, we’ve contemplated making some sort of current regulator for our drivetrain to prevent popping circuit breakers. with the ciruit board, we may finally have a chance to use that idea.
Are the electrical specs available anywhere for download, I can’t find section 2 of the robot manual. I am excited about the circuit board also. Joe, you mentioned knowing currents and speeds, how do you plan on relaying this info back to the player station?
I finally found Section 2 of the manual, and it sheds little light on the Custom Circuit Board.
I wonder if it has to be a hand soldered piece, or if you can go out and make a comercial PCB?
It doesn’t sound like you can since that would NOT be from Digikey…though if you went out and bought the copper clad board and etched it yourself, it might be fine.
Also, it looks as though ALL the custom work being done with this board MUST be contained on the board and within the walls of the Box. So if a wire wants to have say a current sensor on it, it seems the wire must come “through” this box…since the detector would have to be within the walls of the box.
I am planning on making a counter curcuit and a timer to get speed in a digital format then using poor man’s Digital to Analog Converter (I think a resistor network could work) to input a voltage to the sensor port.
I have to see how much $100 buys and what it buys.
60 weeks of stuff to do… …6 weeks until ship date…
Did you find this section online? If you did, where is it?
For a current sensor one method is to use a low-ohm shunt to convert the current flowing thru the shunt to a voltage that could be measured. 10 gauge wire has about 1 ohm/1000 ft so you could use say 10 ft of 10 ga. wire with a “sense” wire at each end of the 10ft shunt. If we want to measure currents in the 20 to 60 Amp range…
V=IR (voltage=currentresistance)
V=20 Amps*.001 ohms (1ohm/1000ft10ft)
V=.2 volts for 20 Amps to .6 volts for 60 Amps would be our signal. That sounds like it is big enough to do something with. But how much power would be lost in the 10 extra feet of wire?
W=I^2R (Watts=current squaredresistance)
W=60^2.001 60 amps worst case
W=3.6 Watts, I can live with that.
Now what to do with the signal? How do you get the info back to the driver?
Originally posted by Allen Smith *
**For a current sensor one method is to use a low-ohm shunt to convert the current flowing thru the shunt to a voltage that could be measured. 10 gauge wire has about 1 ohm/1000 ft so you could use say 10 ft of 10 ga. wire with a “sense” wire at each end of the 10ft shunt. If we want to measure currents in the 20 to 60 Amp range…
V=IR (voltage=currentresistance)
V=20 Amps.001 ohms (1ohm/1000ft10ft)
V=.2 volts for 20 Amps to .6 volts for 60 Amps would be our signal. That sounds like it is big enough to do something with. But how much power would be lost in the 10 extra feet of wire?
W=I^2R (Watts=current squaredresistance)
W=60^2.001 60 amps worst case
W=3.6 Watts, I can live with that.
Now what to do with the signal? How do you get the info back to the driver? **
Umm… I think you missed a decimal point somewhere. Remember that
P=IV, so if you are pulling 60 Amps over a drop of .6 volts, that is
60 * .6 = 36 Watts, NOT 3.6 Watts. I’m not sure if 36 Watts is worth it…
If you look at the additional hardware list under the “Control System” section, it lists “Custom Circuit Board”. This tells me I can print and etch a PCB without including the cost in the $100 limit.
*Originally posted by Ed Sparks *
**If you look at the additional hardware list under the “Control System” section, it lists “Custom Circuit Board”. This tells me I can print and etch a PCB without including the cost in the $100 limit. **
The manual says “Electronic Components Up to $100 worth from Future FAI or
Digi-Key” then at a different line, it says “Custom Circuit Board must fit inside Plastic Enclosure for Custom
Circuit Board (see below), qty 1”
Express PCB http://www.expresspcb.com/ExpressPCBHtm/Costs.htm can do the PCB for as little as $59 incl. shipping (for a 3.8" x 2.5" board). However, I do not think the PCB cost is included in the $100 limit nor do you have to buy it from FAI or Digi-Key. BTW, they also give you software to design the circuit
Express PCB http://www.expresspcb.com/ExpressPCBHtm/Costs.htm can do the PCB for as little as $59 incl. shipping (for a 3.8" x 2.5" board). However, I do not think the PCB cost is included in the $100 limit nor do you have to buy it from FAI or Digi-Key. BTW, they also give you software to design the circuit
-kai **
I don’t think that counts…I think the idea is that you can either hand solder the proto…or you can perhaps buy the plated FR4 material and etch your own PCB if you want. (if you buy the materials from one of the approved suppliers…at least the FR4 I would think)
IMHO, use of an outside “Rapid Prototype” service for production of a custom PCB is OK. Many team even use outside services in the production of the robot. It’s all on the up and up. It’s a matter of how your team chooses to “Inspire”.
In my opinion, page 13 of the rules says that “inputs to the circuit board may be…optical sensors, motors and OTHER SENSORS ALLOWED IN THE ADDITIONAL HARDWARE LIST.” And since components that could be used as sensors are availible from Digi-Key I would assume they could be external to the PCB. So an optical sensor purchased from Digi-Key can be placed on a wheel, arm or other part of the robot and wired back to the PCB board.
At least that is how I would interpert that section.
( Don’t be wimps… etch your own PCB!!!)
Steve Alaniz (Mentor)
“…you’re saying we can look forward to robots demanding higher saleries and behaving badly…” - Sally Forth
I have previously read some stuff on etching PCB and used a small breadboard a few times but I never really etched PCB.
Would you use FR4 (not like I have any idea what it is) or a Copper Clad Board to etch?
OK, I was joking… etching a PCB is not for the faint of heart. I understand the San Jose guys really pushed for adding PCB and I suspect other people who had access to professional facilities also liked the idea. I do too, but I’m just a hobbiest from WAY back and I’ve ruined quite a few shirts from etchant.
You can get a copper clad board from Digi-Key or Radio Shack, draw or dry transfer your circuit pattern on the PCB, drill the holes for the ICS and wires, (there’s also a photo etch method but you can’t see where to drill the holes…) pour either Ferric Chloride or Sodium Persulfate or Ammonium Persulfate in a PLASTIC or GLASS tray, place your PCB in the solution and rock it for about 20 minutes or until the solution has etched away all the unwanted copper, clean the copper with fine steel wool and VIOLA! (Luck helps here… sometimes you etch away a WANTED circuit line if you’re not careful) Now all you have to do is figure out how to properly dispose of the spent etchant…
OR… you can WIRE WRAP the circuit on a perf board. (Don’t laugh… I wire wrapped an entire clone FIRST controller system in 1998…also not for the faint of heart or anyone who has a life!)
If you’re STILL heck bent… go to the library and check out the December 1989 copy of Radio-Electronics and build the tank system they suggest… for NEXT year.
Good Luck!
Steve Alaniz
“Yeah those robots are cool…but If you can’t play Nintendo on them… what good are they?” - Hilary Forth
