Troubles with L297/L298

[ragrillo]

Phil

I made a new board where I can change easily the L298, without soldering, to compare different chips.

In this new board I have:
L298
7805
2 sensing resistors
Inputs for the logic pins (Input 1, 2, 3, 4, EnabA and EnabB)
4 outputs

Each logical input is connected to ground through a 5K6 resistance and to a switch to 5 V.

There are no shorts between any pins in this board.

I connected the outputs to +Vs (27.2 V) through resistences of 600 ohms and 1K.
I tested two different chips used in the first board, and the results was about the same (The differences were no more than 0.4 V in the outputs)

The readings where, with the EnableA and EnableB low

1) With all the logical inputs low 21.2 V in all the ouputs
2) With Input 2 Hi 20.5 V in all the ouputs
3) With Input 4 Hi 12.2 V in all the ouputs
4) With Input 4 and 2 Hi 11.5 V in all the ouputs
The inputs 1 and 3 has not effect in the readings.

Putting the Enables Hi make the readins be 0.2 V less in all the cases.

If I put the control tension Vs in 0 volts, there are not effect in the readings. Do you know what all of this mean?

Raúl

[pminmo]

Well,
It made sense that you had blown chips until you said with Vs at 0 volts you had no different readings. Just to make sure were on the same assumptions:
1. Vss is 5VDC (pin 9) and Vs is 25vdc (pin 4)?
2. Gnd is pin 8?
3. Add the ground for the 5vdc power and the 25vdc power is connected together?
4. You do have 5VDC on Vss (pin 9) correct?

Phil

[ragrillo]

Phil
The answers are yes for all of the questions.
I will change the L298 and after test it I will tell you what happen.
Thank you.

Raúl

[ragrillo]

Phil
I made a lot of test and when nothing worked, I looked again to my schematic and saw that I made a stupid mistake. I realize that I misunderstand the pins distribution. In my board, the L298 was place as if would be mounted in the botton side. When I did so, every thing start working.
Anyway, I am just starting to understand how it works, but I did not install the stepper yet. May be I will ned some help when I connect it.
Thanks a lot for your help

Raúl

[pminmo]

Great! Glad you figured it out. I assumed that the CAD tool you were using had the model correct. Although that was one reason I wanted you to use a proto board or vector board just to try the chip, in case there was a problem with the board.

Phil

[aswin]

send l297/l298 circuit

[pminmo]

Originally Posted by aswin send l297/l298 circuit

schematic, board layout and artwork:

http://pminmo.com/PMinMOwiki/index.php5?title=L297-8

[sreedhar reddy]

i was designed a +24V stepper motor controller using l297 and l298 on ARM(SAM7A3). am using two PMW channels one for clock and other for reference. reference signal is applied to the l297 after filter(R=1k,c= 10Uf). motor is running only at 1 khz frequency. i want to run motor with ramp speed. can any one help me.