Results of the eBlock Wire Experiment

Measured

For each button/led eBlock pair we programmed the pair to communicate at the following baud rates: 1200, 2400, 9615, 125K, and 250K. We connected all the wire available to form a the longest possible double stranded pair of wire (one wire was for ground, the other wire was for data). Then for each button/led pair we tested communication at various lenghts as shown in the table. A "pass" entry in the table indicates sucessful communication between the button/led pair, a "fail" entry in the table indicates failed communication between the button/led pair. The largest length tested was 11,160 feet (approx. 2.1 mile), at which point we ran out of wire.

Wire Length
(feet) Baud Rate

1200 2400 9615 125K 250K

11,160 ft pass pass pass fail fail

7,650 ft pass pass pass fail fail

7,550 ft pass pass pass fail fail

7,450 ft pass pass pass fail fail

7,350 ft pass pass pass fail fail

7,250 ft pass pass pass fail fail

7,150 ft pass pass pass fail fail

7,050 ft pass pass pass fail fail

6,950 ft pass pass pass fail fail

6,850 ft pass pass pass fail fail

6,650 ft pass pass pass fail fail

6,000 ft pass pass pass fail fail

5,000 ft pass pass pass fail fail

4,750 ft pass pass pass fail fail

4,650 ft pass pass pass fail fail

4,550 ft pass pass pass fail fail

4,500 ft pass pass pass pass fail

4,350 ft pass pass pass pass fail

4,250 ft pass pass pass pass pass

4,000 ft pass pass pass pass pass

3,500 ft pass pass pass pass pass

Estimated

Since for several baud values we ran out of wire before the communication failed, we decided to do an estimation to see how far it may be possible to communicate.

Assumptions Made:

Range for a bit to be considered high is Vdd-0.7 to Vdd

Range for a bit to be considered low is 0 to 0.6

I_oh = 3.0 mA when Vdd = 4.5 V and -40 degrees to 85 degrees celsius

I_ol = 8.5 mA when Vdd = 4.5 V and -40 degrees to 85 degrees celsius

Assume only travel on 22 gauge wire with resistance of 16.8 ohms/1000 feet

High Bit -
R = (4.5 V - 3.8 V) / 3.0 mA
R = 233.33 ohms

233.33 ohm / 16.8 ohm / 1000 ft
D = 13,888 ft

13,889 ft / 5280 ft/mile
D = 2.63 miles

Low Bit -
R = (0.6 V - 0 V) / 8.5 mA
R = 70.6 ohms

70.6 ohm / 16.8 ohm / 1000 ft
D = 4201.68 ft

4201.68 ft / 5280 ft / mile
D = 0.796 mile

From the measured experiments it is obvious that we were able to communicate more than 0.7 miles, thus we expect that a zero value can be detected for a range greater than 0 to 0.6 V for this device and would thereby increase the estimated communication distance.

Wire Length (feet)	Baud Rate
Wire Length (feet)	1200	2400	9615	125K	250K
11,160 ft	pass	pass	pass	fail	fail
7,650 ft	pass	pass	pass	fail	fail
7,550 ft	pass	pass	pass	fail	fail
7,450 ft	pass	pass	pass	fail	fail
7,350 ft	pass	pass	pass	fail	fail
7,250 ft	pass	pass	pass	fail	fail
7,150 ft	pass	pass	pass	fail	fail
7,050 ft	pass	pass	pass	fail	fail
6,950 ft	pass	pass	pass	fail	fail
6,850 ft	pass	pass	pass	fail	fail
6,650 ft	pass	pass	pass	fail	fail
6,000 ft	pass	pass	pass	fail	fail
5,000 ft	pass	pass	pass	fail	fail
4,750 ft	pass	pass	pass	fail	fail
4,650 ft	pass	pass	pass	fail	fail
4,550 ft	pass	pass	pass	fail	fail
4,500 ft	pass	pass	pass	pass	fail
4,350 ft	pass	pass	pass	pass	fail
4,250 ft	pass	pass	pass	pass	pass
4,000 ft	pass	pass	pass	pass	pass
3,500 ft	pass	pass	pass	pass	pass