confused about current sensing resistors

[patriciooholegu]

Hey people.
The last few weeks i was attempting to make work this unipolar stepper driver Sanyo stk6712bmk3 Ic removed from a copier machine. When i look at the datasheet the schematic is very simple and straight forward. The calculations for current sensing are easy but, at the first attempt of moving the stepper...the power source blow-up! bad, so i grab another power supply and again..It Blow up!!!
Now, the calculations are correct, i m sure about that, but looking other driver boards i notice this: Current sensing resistors are mostly those ceramic clear ones. Instead of that i just put a standard type resistor.
Is this the problem?

[LZ1TWB]

Hi, what power supplies are you using? It seemed that they are very low powered as you "blow" them that easily. Have you calculated the current that is needed for your particular schematic?

You may have shorted for some reason the stepper driver, and that would cause the PS to die. Remember that the driver should be permanently connected to the DC side on the capacitors, and turning the power on is accomplished on the AC side. Otherwise there may be problems.

As for the sensing resistor, it is recommended that it's non-inductive type, and of suitable power rating to manage the voltage drop times the current passing through it.

Todor

[Konstantin]

Hi. I have got some stk6713 stepper drives and have been using them with success.
Here is a post of mine with the pic of the drive. http://www.cnczone.com/forums/showpo...2&postcount=10

As I understand, the STK6712 does no uses a "current sensing" the 2 resistor that you must choose simply LIMIT the current. It is a voltage divider circuit.

Here is a configuration I have used on my drives, I am not sure if 6712 and 6713 are pin to pin compatible, but might be, so beware.
Since the STK67(12/13) are 4 phases input I have used l297 to enable the drives to use STEP/DIR signals.


Next time you test something, try using a fuse to save your electronics.

Mach 3 Dir and Step active LOW.

/***********  L297 wiring  *************/

PIN	CONN	NAME
---------------------
1 	NC	SYNC
2	GND	GND
3	NC	HOME
4	PIN_9	ON STK PCB (I wire this through an inverter 74ls04)
5	NC	INH1	
6	PIN_11	ON STK PCB (I wire this through an inverter 74ls04)
7	PIN_10	ON STK PCB (I wire this through an inverter 74ls04)
8	NC	INH2
9	PIN_12	ON STK PCB (I wire this through an inverter 74ls04)
10	+5V	ENABLE ***NC for now***
11	GND	CONTROL (10kOhm resistor to GND pulldown)
12	+5V	Vs			
13	GND	SENS2
14	GND	SENS1
15	GND	Vref	
16	NC	OSC	
17	DIR	CW/CCW	
18	STEP	CLOCK	
19	+5	HALF/FULL (HIGH IS HALF) (10kOhm resistor to +5v pullup)
20	NC	RESET

NOTES:
GND signal must be connected to GND on the BOB board to equalize ground planes. 

/************ PCB  STK 6713BMK4 PCB  *************/
J143 CONNECTOR 
------------
1	GND	
2	GND
3	GND
4	Vcc1 +18 - +42V
5	Vcc1 +18 - +42V
6	Vcc1 +18 - +42V
7	GND
8	Vcc2 +5 IOH SETTING CIRCUIT
9	PIN 13 on STK6713 A  PHASE
10	PIN 15 on STK6713 A' PHASE
11	PIN 14 on STK6713 B  PHASE
12	PIN 16 on STK6713 B' PHASE
13	Vcc2 +5


STK6713BMK4 IC Pinouts
PIN --- NAME
1	 Vcc2
2	 A phase motor output
3	'A phase motor output
4	 PG motor ground
5	 SG motor ground
6	 B phase motor output
7	'B phase motor output
8	 TD1 (motor hold noise reduction use cap with pin 10)
9	 Vref
10	 TD2 (motor hold noise reduction use cap with pin 8)
11	 Vref
12	 NC
13	 A phase input
14	 B phase input
15	'A phase input
16	'B phase input

Standard motor connector J144
PIN --- NAME ---------- MOTOR LEAD COLOR
1	COMMON		BLACK
2	COMMON		WHITE	
3	MOTOR A COIL	RED
4	MOTOR 'A COIL	YELLOW
5	MOTOR B COIL	BLUE
6	MOTOR 'B COIL	ORANGE

CURRENT LIMITING RESISTORS
Formula is Amps = 1.3*(R2/(R1+R2))*(5.2/0.33) (5.2 is my Vref voltage [pin 8 on J143 connector], use your logic [+5 or watever] voltage in the formula for more exact results

Amps --- R1 -- R2  value in Ohms
------------------------------
0.91A - 4700 - 220
0.94A - 3300 - 160
1.07A - 1800 - 100
1.09A - 3900 - 220
1.34A - 4700 - 330
1.46A - 4300 - 330
1.59A - 3900 - 330
1.70A - 3300 - 300
1.86A - 3000 - 300
1.86A - 3900 - 390
2.01A - 3300 - 360
2.03A - 3000 - 330
2.14A - 4700 - 550
2.16A - 3300 - 390
2.18A - 3600 - 430
2.19A - 3000 - 360
2.27A - 2400 - 300
2.32A - 4300 - 550
2.35A - 3000 - 390
2.36A - 3300 - 430
2.36A - 3600 - 470
2.47A - 2400 - 330
2.54A - 3600 - 510
2.55A - 3300 - 470
2.67A - 1800 - 270
2.67A - 2200 - 330
2.67A - 2400 - 360
2.74A - 3300 - 510
2.75A - 3600 - 560
2.82A - 1000 - 160
2.86A - 2400 - 390
2.88A - 2200 - 360
2.92A - 1800 - 300
2.97A - 3300 - 560