Did you hear a “DING” after a flash? 
I often see very bright flashes, but then I lose short term memory for a while. 8)
just so long as you are not pushing pens around on the table with your mind afterwards the effect should be temporary. 
I breadborded some of those switches (like the ones on the Bot Board) and mounted them to the feet on the BRAT. I have tested that the weight of my stock BRAT, (with a pan servo) really has no problem actuating the switches. However, I think using only 3 switch per foot (2 in front and one on the outside in the rear of the foot) is a much better plan. It adds some much needed margin to the design.
If you do want to do the board design… The LED’s can be placed so they shine through the holes in the foot. And the wire connector can be in the hole where there is no LED. I will reimburse you for your costs to have the prototypes built.
So there’s no confusion, can you post a photo of the foot and draw lines to the holes you are refering to? also, wouldn’t the third switch in the rear cause the foot to teeder?
Well I hadn’t tested it yet, but now that I have it’s not a good idea to go with 3 switches per foot. 
Let’s go back to 4 switches. The switches I have are not the lowest pressure ones and they still reliably engage with the weight of the BRAT. So the production run with the lowest pressure switches, I think we will be ok. I’m working on a photo…
Here is an image of my prototype foot switches. I don’t have any LED’s here. But they will be visible from in the round holes in the aluminum foot. I’m ready to abandon the idea of using the PC board alone without the aluminum RF-01.
It looks real good Jim! I am still going to pursue my separate sensor board idea though, because I really think it has more applications than just foot sensors.
8-Dale
It looks like the FOOT contact area is now limited to 4 tiny little switch shafts, instead of the entire foot area. Not good, in my opinion.
I’d suggest (as Mike and I discussed earlier in this thread) that the switch shafts, push pins, or levers go THROUGH the foot, such that the travel of the actuator is limited (to protect the switch) when the foot finally makes contact with the surface, and to transfer the weight onto the foot, rather then remaining on the switch. This way, the full foot rests on the surface.
Alan KM6VV
Fair enough. But the question is, will the switches handle the weight of the bot without damage, and I think they will. Well anyway, that’s what prototypes are for.
If the switches are at each corner like Jim has in the photo, it’s no different than four legs of a table which is solid unless one of the legs is of a different length of course. If it proves to be a problem during testing, then material the thickness of the switch body minus the height of the button can be added to the bottom of the foot, perhaps a piece of lexan the shape of an “X” on the bottom to where it just fits inside the open area of the foot. If it proves to be fine the way it is, then I don’t see a need to worry about it. The bots run generally slow anyway so it’s not like the bots are going to be running with these switches. The slow gaits would allow plenty of time for the 4 switches to make contact before the full weight of the bot is applied.
This is just my thinking anyway. 
are those 6mm sq. tactile switches?
If those are the switches I think they are then I have the foot print in Eagle cad ready to go.
Yepper. I am also thinking of a very soft rubber material being applies to the bottom of the PC board. As long as it doesn’t interfere with the switches engaging.
Files have been emailed BTW.
I agree.
This might require adding some holes to the ARF-01/ARF-02 feet, but it would be a better design in my opinion. This could be accomplished with my idea also, by changing where the sensor boards are mounted. The full wait of the robot should never be on the switches, which should move just enough to make contact. With my idea, you could also position the sensor boards so that they hang over the foot where the switch could point downward and not have the full robot weight on the switch at any time.
8-Dale
OK I have been thinking about the button circuit and the general desire to KISS the concept.
If you switch GND then you probably need a circuit similar to what you drew up.
But if you switch the +5V then you can put in parallel
- a series resistor and green LED to ground, and
- a weighted resistor to a summation node.
So long as the voltage at the node does not get close to Vf of the LEDs then you should be OK.
You may want to include a single non-inverting op-amp at the output to increase the number of bits you can see between switch states.
Here is a table with the different output voltages for each combination of 4 switches.
switch# R in series
R1 8060
R2 4020
R4 2000
R8 1000
RD 499
V 5
8-bits 256
binary resis- divider
value tance volts
0 0.000
1 8060 0.292
2 4020 0.552
3 2682 0.784
4 2000 0.998
5 1602 1.187
6 1336 1.360
7 1146 1.517
8 1000 1.664
9 890 1.797
10 801 1.920
11 728 2.033
12 667 2.140
13 616 2.238
14 572 2.330
15 534 2.415
V15-V14 = 0.085 volts
Vbit = 0.020 volts
min step = 4.375 bits So if you put a simple x2 amplifier you would easily see 8 counts between steps which should be plenty.
I can add that to the schematic, but what about what I have so far? I copied Jims original hand drawn schematic and made it a little simpler. The power for the hex inverter are pins 7 and 14 which is not shown but the Eagle cad software automatically connects power and ground to these pins. When looking at the schematic, keep a mental note pins 7 & 14 are connected to power and ground.
Jim’s original schematic does not show pins 7 & 14 connected to anything but the Hex Inverter that I am using is an SOIC14 component.
check yahoo, I sent a paint rendition of what I am talking about.
Ok here it is converted over to Eagle Cad. Its ready to be layed out and banged out.
This is another option for Jim to consider.
heh, you lost all the values on the resistors.
ya know I was thinking about the LEDs interfering slightly with the summing network and I have a solution… blue LEDs have a higher forward voltage so instead of green use blue LEDs… and you get the bling look for free.