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Topic: What can Arduino MICRO input pins be used for? (Read 1 time) previous topic - next topic

32bit

#15
Apr 21, 2017, 08:29 am Last Edit: Apr 21, 2017, 08:34 am by 32bit
While the Darlington is continuously turned on and off by the PWM signal, the RC low pass filter will result in a minor ripple of the voltage on the cap. With a H-bridge output the bridge should be turned off when the voltage difference becomes lower than some arbitrary amount, depending e.g. on the ADC resolution.

In the given circuit, with a 5V supply, no negative voltages can occur.
Changed the output circuit to match logic


Thinking I would need an Arduino input and output for top Voltage follower,
And a second Arduino PWM output with the same reference and half the on-time.
Hope I am keeping up, their is a lot to learn.

I do not have a good understanding of H-Bridge.
When you say switch off, do you mean less on time.
Or is this a feature of H-bridge isolation when voltage is reached.

I am a slow learner, but everything sinks in with time.




DrDiettrich

Don't forget the feedback. You need at least a digital P controller, eventually a PID controller.

In a H-bridge one or none transistor can be on at a time. In TTL terms it has a tri-state output.

32bit

#17
Apr 21, 2017, 12:29 pm Last Edit: Apr 21, 2017, 02:47 pm by 32bit
Don't forget the feedback. You need at least a digital P controller, eventually a PID controller.
Sorry, you lost me here with feedback and needing digital P controller, eventually a PID controller.
I searched for P controller and only found PID controller, what do you mean.
Are you referring to Arduino code to test the output against input?

I was thinking analogRead and analogWrite covered requirements

Reading: https://www.pdx.edu/nanogroup/sites/www.pdx.edu.nanogroup/files/2013_Arduino%20PID%20Lab_0.pdf

The input voltage from divider is the variable set point.
Only user adjustment feature, to be set once before tests,
increments up to 100 millivolt gain adjustment to the first followers output voltage.
The logic has to follow through as with the circuit logic with op-amps

DrDiettrich

It might be the right time now, to make your hands dirty, and to come back with more specific questions.

32bit

I posted before seeing your reply, this might include additional questions?
Not sure if I have understood what you were explaining

DrDiettrich

A voltage follower requires feedback from the driven circuit, and thus is a controller, regardless of analog or digital implementation. It can be implemented as simple as in #10 (Proportional controller), or as a full fledged PID controller.

32bit

#21
Apr 21, 2017, 06:25 pm Last Edit: Apr 21, 2017, 07:02 pm by 32bit
A voltage follower requires feedback from the driven circuit, and thus is a controller, regardless of analog or digital implementation. It can be implemented as simple as in #10 (Proportional controller), or as a full fledged PID controller.
I have enough information to know Arduino can cover the task.
The programming seems to be Basic with different words, no problems.

Here is a tool: RC Low-pass Filter Design for PWM.
http://sim.okawa-denshi.jp/en/PWMtool.php

Arduino Micro Board with Headers $33.86 including freight
https://www.freeshippingtech.com.au/product/SEVARD0005/Arduino-Micro-Board-with-Headers

Just to confirm, this and a standard USB chord is all that's required?

DrDiettrich


32bit

No.

The analogue input can't read negative voltages. You have to bias it at 2.5V, so that bias is carried over when you do the read / write.
I would like to know how you are getting the 2.5v bias?
Because I am having some hiccups in design and looking for the simple alternatives!

-----------------------

My idea at present is to Multiply the divider voltage by 4 through resistor values.

Starting with the original baseline voltage division:
62.05v 132000/82500 ohm 3.65v
42.5v  132000/82500 ohm 2.5v

Lift Voltage divider output by factor of 4:
62.05v 132000/40600 ohm 14.6v
42.5v  132000/40600 ohm 10v

This widens the output voltage differential from 1.15v to 4.6v.

If I can supply 10v to the op-amps (-) input,
this should give an output of at 0v corresponding with the original 2.5v division,
And 4.6v corresponding with original 3.65v division.

Not sure how this would be done otherwise?

--

This would only just fit within the op-amps specs, with an increased supply voltage.
If I can create an accurate reference and it works, an extra voltage regulator is not a problem!

TL082 Dual JFET-input op-amps
Max Supply voltage 18
The magnitude of the input voltage must never exceed the magnitude of the supply voltage or 15 V, whichever is less.

Open to surgestions

 
 

Grumpy_Mike

Quote
I would like to know how you are getting the 2.5v bias?
By a 10K pull up and a 10K pull down on the analogue input, then you normally AC couple it, but I suspect you might not want to do that.

32bit

My solution at the moment is op-amp with adjustable reference.

using this logic:
Starting with the original baseline voltage division:
62.05v 132000/82500 ohm 3.65v
42.5v  132000/82500 ohm 2.5v

Lift Voltage divider output by factor of 4:
62.05v 132000/40600 ohm 14.6v
42.5v  132000/40600 ohm 10v

------------------

Numbers are just to show how adjustment widens variation voltage from 1.15v to 4.6v as example.

I am happy with this as a solution, but persisted a little longer thinking Arduino users would have come up with a low voltage solution to such situations?

It would seem not, or at least not with the same simplicity.

Thank you for the guidance.

Grumpy_Mike

Quote
I am happy with this as a solution
Good because I for one have no idea what this solution is. No schematic == no idea what you mean.

Quote
but persisted a little longer thinking Arduino users would have come up with a low voltage solution to such situations? It would seem not,
This is because what you are doing is so bazaar as to be verging on the insane, and no one who knew anything about electronics would even consider this. Wrong tools for the job. It is like having a dentist remove your teeth with a sledgehammer.
 

DrDiettrich

From the entire discussion I guess that the project is purely academic (abstract). If the target is a power supply, it will require more components for reliable operation, and more thought about practical electrical problems.

allanhurst

What are you actually trying to acheive? a split rail psu?

Allan

32bit

The Question is Abstract.
I can see a lot of applications for Arduino, because unlike a timer and counter it has programmable inputs.

My question, was how do you interface with full resolution from a less then 5v differential input?
Without having to amplify the voltage outside 5v IC circuitry!

What do you use as alternative, I can study the datasheets with an IC name.
Not fussed if the question has not got an answer, don't shoot me down for asking.



 

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