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<set_>
ds2: So, if the am335x GPIO pins go HIGH/LOW at 2.65v, what is the definitive cure in the form of math? I mean, say...
<set_>
my op-amp, and no to the switch for now of the BJT, needs to be accepting of 4.5v at least for the "OPTO" switch to turn on the driver.
<set_>
If you ever get around to the build of it all, please let me know. Struggling with simplicity and simplification over here (and at the same time)!
<set_>
Let me get a circuit on photo.
<set_>
Please hold.
<set_>
This will take a lifetime. Forgive me. I need to brush up.
<set_>
Okay!
<set_>
I think I made sense out of what I "accomplished..."
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<set_>
There is a driver between the motor and op-amp.
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<set_>
So, 3.3v is actually 2.65v when the GPIO goes HIGH and my divider circuit is bunk because it causes current of 1.65v. Blah. I am pushing current at 1.0v. Ha.
<set_>
That does nothing to this driver.
<set_>
So, this was my best guess until knowing it. "I hold the GPIO HIGH" while the motor moves and then change direction.
<set_>
Man, time flies.
<set_>
I should have measured my divs.
<set_>
Basically, I am trying to make sure the board does not die while attempting glory. A lost pin or two is not big deal (sort of) but oh.
<lucascastro>
measure the voltage without any circuit biased
<set_>
!
<set_>
so, apply the measurement without the op-amp or the voltage divider is what you are saying or just the voltage divider needs to be not applied?
<set_>
I thought the GPIO when HIGH was 2.65v of current...
<set_>
rising...sorry.
<set_>
Not HIGH, rising.
<lucascastro>
is not that god drive current though GPIO
<lucascastro>
But measure the voltage without any circuit.
<lucascastro>
op-amp or voltage divider.
<set_>
lucascastro: I am driving two GPIO pins and a 5v pin from the BBG to the op-amp to the driver...
<set_>
I have a voltage divider on each GPIO to sway away from EMI.
<lucascastro>
I don't know about the BBG I only own BBB, so you can read the spec of BBG and look for the maximum current through the board/GPIO
<set_>
am335x
<lucascastro>
calculate your circuit how current will drive.
<set_>
It has the same am335x.
<set_>
Okay...I will calculate how the current drives.
<set_>
I guess I need to find the BBB now.
<set_>
Maybe this board is different.
<set_>
So, one end to the other and then end it. Got it. Okay.
<lucascastro>
op-amp is good because you can use external power-supply.
<set_>
3.3v (2.65v rising) GPIO to voltage divider (1000k and 10000k equal 1.65v of current when HIGH) and then partially GND and then to op-amp (inverting or non-inverting (my choice)). Like this?
<lucascastro>
R (1M and 10M) ?
<set_>
3.3v (GPIO) goes to op-amp(inverting) and the ... No.
<set_>
k
<set_>
Oh.
<set_>
1k 10k
<set_>
Sorry.
<set_>
Blah.
<set_>
So, then GPIO goes to op-amp and then GPIO to voltag divider goes to op-amp and GND.
<lucascastro>
ap-omp parallel to voltage divider?
<set_>
On my LM358N, it states inverting and non-inverting but yes.
<set_>
I have two outputs on the op-amp.
<lucascastro>
if parallel to voltage divider, maybe depends how your op-amp is setup, boards ends up fed current through op-amp.
<set_>
So, the GPIO to voltage divider to op-amp on one pin of the op-amp.
<set_>
Right.
<set_>
That is what I was afraid of now.
<set_>
Because of the voltage divider, it never reaches above 1.65v.
<lucascastro>
are you going to driver motor? Why not use the external power-supply over the op-amp?
<set_>
yes.
<set_>
I was...but I have a driver.
<set_>
The driver is for a two-phase motor.
<set_>
I have two GPIO pins controlling dir/step and then a 5v supply on an optocoupler type connection to the driver.
<set_>
So, my op-amp provides (supposedly) enough current and amperage via the GPIO pins on the am335x supported BBG to make the motor in an enabled/disabled state, step/dir, and to get recognized by the BBG.
<set_>
The driver is supposed to do the rest...
<lucascastro>
My guess, if you have a circuit driver, it supposed just a voltage signal, not really driver the current, the current go through the 5v that supplied the driver.
<set_>
Right. it is a driver for 5v supplies.
<set_>
Oh.
<set_>
I just understood what you typed.
<set_>
Dang it, okay. But, the step/dir pins need 4.5v minimum.
<lucascastro>
maybe I'm not that clear.
<set_>
I think. Dang it. Let me double check.
<set_>
I got you.
<lucascastro>
What's the meaning of "Dang it"?
<set_>
Darn
<set_>
Or maybe... I mean something like I did not check that already and am having a epiphany.
<set_>
This is what the driver datasheet says: Pulse signal: Pulse active at rising edge; 4-5V when PUL-HIGH, 0-0.5VwhenPUL-LOW.Minimal pulse width of 2.5μs. Add a resistor for current-limiting at +12Vor +24Vinput logicvoltage (1K for +12V, 2k for +24V). The same as DIR and ENA signals.
<set_>
...
<set_>
So, I was trying to amplify the voltage to suit my needs.
<set_>
I got to amplification without movement which caused the heat.
<lucascastro>
So, seems like you need just the signal 4-5v over BBG. The resistance and current control is though the power supply biased to the driver. I'm not english native, but it was what I got.
<set_>
Okay.
<set_>
No issue about your English. I was not born in England either.
<lucascastro>
The driver is powered with 12V and 1K
<set_>
Yea...I saw that sir.
<lucascastro>
Let me know if it worked.
<set_>
I usually put in about 12.4v at 1.2A.
<set_>
That is to power the driver. Then, to supply the Rise of the GPIO...
<set_>
Got you again.
<lucascastro>
That's for the driver that control the motor.
<set_>
Oh. so, the motor accepts 4 to 5v.
<set_>
Aw.
<lucascastro>
If I'm not wrong, the driver has its power-supply
<lucascastro>
not?
<set_>
Yes. I supply it with power.
<lucascastro>
The driver accept a signal at some pins.
<set_>
It is a dead driver without PWR and GND which I supply from a bench supply.
<set_>
Yes.
<lucascastro>
that pins is connect to the BBG
<set_>
yes.
<lucascastro>
So, it was be working
<set_>
Nope.
<lucascastro>
I really don't no way not.
<set_>
The logic signal current is at 7mA.
<set_>
That logic signal current is at 7mA to the driver...
<set_>
nominal/typical is 10mA.
<set_>
hence, my rendition of odd circuits to supply the demand.
<lucascastro>
if the drivers has a FET/MOSFET over the signal pins, it would tried direct biased.
<set_>
Okay.
<lucascastro>
But.
<set_>
But?
<lucascastro>
If you have op-amp, you can use a 5v for op-amp supply
<set_>
Oh.
<set_>
I can use 3.3v for these op-amps.
<set_>
I can try 5v, I guess.
<lucascastro>
but the driver as you mentioned it's require 4-5v
<lucascastro>
for signal
* jkridner
waves to ds2 ... nice to see you active in here.
<lucascastro>
then it's required you supply your op-amp though 5v external supply.
<set_>
lucascastro: okay.
<set_>
I will attempt that idea.
<set_>
Is there a way to control the GPIO pins so that I do not harm the processor on board?
<lucascastro>
so when you get 5v at out of op-amp, it should work.
<set_>
Aw!
<set_>
Okay.
<lucascastro>
yep.
<set_>
i will test until my heart is content!
<lucascastro>
almost use a mosfet as turn on/off button, but you can set the op-amp for that.
<set_>
Right.
<lucascastro>
The op-amp it's a really good way for that shifting.
<set_>
That is what I thought. It accepts two "unbiased" pins from the BBG and outputs one signal.
<set_>
But, I added bias for no reason (pin protection).
<lucascastro>
that I look at op-amp datasheet
<lucascastro>
really common for the external power
<set_>
Okay. If you get bored, look here: LM358N from TI.
<set_>
It can go as low as 3v.
<lucascastro>
Okay, I had wrote wrong, the idea was for you take a look, but I'm doing
<set_>
No...do not. No issue.
<set_>
3v minimum.
<lucascastro>
So, it's really common, you have the gnd(4) and Vcc(8) for external supply.
<set_>
Right.
<lucascastro>
so you put the 5v there you'll get 5V at output
<set_>
Right, that was the issue...
<set_>
I was trying to create the "more-complicated" level shifter with voltage and amperage amplification.
<lucascastro>
hadn't you fed the op-amp?
<set_>
Yes.
<set_>
3.3v
<lucascastro>
so you fed with 3.3v. you will just get maximum 3.3v at output.
<set_>
Are you sure...?
<lucascastro>
yes.
<set_>
Okay.
<set_>
I will test it.
<lucascastro>
The Vcc is not the BBG voltage, it's a external voltage.
<set_>
Oh.
<set_>
I was not aware of this fact.
<set_>
I will review the datasheet again. Thank you.
<lucascastro>
At the input you'll need BBG gnd and GPIO pins for signaling .
<set_>
Right.
<set_>
So, I need to worry about EMI now with the circuit if things go the wrong way.
<lucascastro>
And that it's not going damage your BBG because the required current comes through external power
<set_>
Hmm. Are you sure?
<lucascastro>
Yes,
<set_>
I will test it. Thank you.
<lucascastro>
That's why the ap-omp is really good for that propose.
<set_>
I thought the 5v has to come from the BBG and to use a level shifter of sorts so that the two biased voltages do not intersect?
<set_>
Thank you. I was dead wrong.
<set_>
Okay! Whelp, it is 10:00 in three minutes and I need rest. Peace to you, brother.
<set_>
Testing will ensue.
<lucascastro>
Okay
* set_
says lucascastro saves the year of blabber mouth set_!
<lucascastro>
If you look at the op-amp diagram, all the current comes from the vcc
<set_>
Right...
<set_>
I thought that was the BBG and not a 5v supply.
<set_>
Sir, where would I get a 5v supply?
<set_>
I mean...I would have loved if the BBG or newer boards had the built in GND for 5v.
<set_>
Then, one could test their circuits with 3.3v and do some neat work.
<lucascastro>
you can use other external for testing, and after get it working, you make divider and share with the driver board.
<set_>
Oh.
<set_>
Okay.
<lucascastro>
But it's not good driver current through uc