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RoboNova - Low Voltage Warning Circuit

14 August 2008
Added the two resistors missing resistors but it doesn't really work.
The reason the resistors are not included on the C3024 board is the circuit doesn't work! By the time the voltage drops to 5.8v the regulator has run out of headroom and the processor voltage starts to drop so the test only just works, sometimes!


04 October 2006
I borrowed a RoboNova from Milford Instruments to see what it could do.
First off I was really disapointed with the response from the hand controller, there was such a delay RoboNova was almost unuseable except for demonstrating on a boardroom table.

Looking at the 'Overall Tempate Program(Version 1.00 20051115).bas' it was easy to see why.
The low voltage battery test was always being done because

Editing, recompiling and downloading didn't make any difference!!!!! This time it was because the value returned for 'A' from AD(6) was less than 148. I couldn't find a way of debugging the value of 'A' back to the computer so I did a binary search for values which were less than the result of AD(6). 88 is the value when the battery is fully charged, but it soon drops so I settled on 80.

Now the response to the IR controller was snappy. But RoboNova still wasn't responsive during moves so I added a couple of lines in MAIN: to blink the blue LED to let me know when RoboNova was ready for a new command.

Original code

'================================================
robot_voltage:						' [ 10 x Value / 256 = Voltage]
	DIM v AS BYTE

	A = AD(6)
	
	IF A < 148 THEN 				' 5.8v
	
	FOR v = 0 TO 2
	OUT 52,1
	DELAY 200
	OUT 52,0
	DELAY 200
	NEXT v
		
	RETURN
'================================================

My modified code

'================================================
robot_voltage:						' [ 10 x Value / 256 = Voltage]
	DIM v AS BYTE

	A = AD(6)
	
	IF A < 80 THEN 				' 148=5.8v
		FOR v = 0 TO 2
		OUT 52,1
		DELAY 200
		OUT 52,0
		DELAY 200
		NEXT v
	  endif
	RETURN
'================================================

Blink blue LED in MAIN:

'================================================
MAIN:
OUT 52,1			'blue LED OFF
GOSUB robot_voltage
'GOSUB robot_tilt
OUT 52,0			'blue LED ON

I also added a history section for code modifications.

'-----------------------------

'History
'2006-07-09 robot_voltage:
'			missing ENDIF before RETURN
'			maximum AD(6) is 88 on fully charged battery
'			not 148 as in original code
'			test set at 80 as quite quickly 88 is too high
'2006-07-09 MAIN: added LED blink in so we can tell when robot is ready to receive IR cmnds
'			OUT 52,1			'blue LED OFF
'			GOSUB robot_voltage
'			GOSUB robot_tilt
'			OUT 52,0			'blue LED ON

'================================================

Missing resistors
I have just come across Matt Bauer's RoboNova pages and his page on the Low Voltage warning Circuit. He says the circuitry to make the low voltage warning circuit work is not fitted as standard and refers to page 95 in the manual. It is only two resistors and two connectors. The pin out of the connectors is not in the printed manual nor in the PDF ( did Hitec have a zillion pixel screen to view the PDF?! Really unuseable as you have to keep scrolling sideways as well as up and down). Apparently though 0v is on the AD6 port and +V is on S11. ( I haven't yet tried the modification). Still the test seems to work ok indicating when the battery is low without it, it is just that the AD6 value is much lower (so how does it actually work without the two external resistors?).

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