http://electronics.stackexchange.com/questions/43498/how-can-i-use-a-12-v-input-on-a-digital-arduino-pin

A simple resistor divider will bring the 12 V down to the 5 V an Arduino can digest. The output voltage can be calculated as ………

Better Michael’s optocoupler is a good alternative, though a bit more expensive. You often will use an optocoupler to isolate input from output, but you can also use it to protect an input like you want here. ………….

for my money’s worth , if I don’t want any stuff ups in the future I would use the opto coupler every time – its guaranteed not to stuff the arduino because it is using the arduino’s own power source to power the input side

I would see if you can buy a dedicated opto coupler for the arduino

wookiemeister said:

http://electronics.stackexchange.com/questions/43498/how-can-i-use-a-12-v-input-on-a-digital-arduino-pin

A simple resistor divider will bring the 12 V down to the 5 V an Arduino can digest. The output voltage can be calculated as ………

Don’t use 5V input to an Arduino unless you have a regulated power supply or can otherwise guarantee the voltage. Use the VIN input which happily accepts anything from 6V to 12V and does its own internal down-regulating.

mollwollfumble said:

wookiemeister said:

http://electronics.stackexchange.com/questions/43498/how-can-i-use-a-12-v-input-on-a-digital-arduino-pin

A simple resistor divider will bring the 12 V down to the 5 V an Arduino can digest. The output voltage can be calculated as ………

Don’t use 5V input to an Arduino unless you have a regulated power supply or can otherwise guarantee the voltage. Use the VIN input which happily accepts anything from 6V to 12V and does its own internal down-regulating.

adafruit seem to recommend always using a dedicated specialised power supply to feed the arduino regardless of the arduinos capabilites

>A simple resistor divider will bring the 12 V down to the 5 V an Arduino can digest

if the output from the device generating pulses had an open collector PNP and pulls up a simple divider will stop the signal from going all the way down to the off state in which case it may not reach some trigger or reset threshold reliably, however if it had an open collector NPN and pulls down it wouldn’t be an issue.

mollwollfumble said:

wookiemeister said:

http://electronics.stackexchange.com/questions/43498/how-can-i-use-a-12-v-input-on-a-digital-arduino-pin

A simple resistor divider will bring the 12 V down to the 5 V an Arduino can digest. The output voltage can be calculated as ………

Don’t use 5V input to an Arduino unless you have a regulated power supply or can otherwise guarantee the voltage. Use the VIN input which happily accepts anything from 6V to 12V and does its own internal down-regulating.

It isn’t for the power supply. It is for a digital input.

wookiemeister said:

morrie said:

transition said:

>stop it or you’ll go deaf

Morrie, suppose that neat little arduino chip you’re using has a schmitt trigger(or similar) you can adjust for tidying up and managing signals in.

You can do stuff like de-bouncing in the software. It is running at 16 MHz. There is a chapter in my guide book about that but I haven’t had cause to use it so far.

the last thing I read was they were using delay() to rid bounce

morrie said:

wookiemeister said:

morrie said:

transition said:

>stop it or you’ll go deaf

Morrie, suppose that neat little arduino chip you’re using has a schmitt trigger(or similar) you can adjust for tidying up and managing signals in.

You can do stuff like de-bouncing in the software. It is running at 16 MHz. There is a chapter in my guide book about that but I haven’t had cause to use it so far.

the last thing I read was they were using delay() to rid bounce

Yes, but there is a library function that does it in a more sophisticated way.

if we are still talking your motor output signal

wouldn’t that be fairly clean – assuming its being done electronically?

morrie said:

morrie said:

wookiemeister said:

You can do stuff like de-bouncing in the software. It is running at 16 MHz. There is a chapter in my guide book about that but I haven’t had cause to use it so far.

the last thing I read was they were using delay() to rid bounce

Yes, but there is a library function that does it in a more sophisticated way.

most likely a time based function that compares one part of a wave to another

millis() might be involved

wookiemeister said:

if we are still talking your motor output signal

wouldn’t that be fairly clean – assuming its being done electronically?

It is an encoder signal. I think it is relatively clean. The VFD accepts it without any problems. I haven’t put my Picoscope onto it.

it might say lets look at it over 50 millis()

whats going on with the wave , whats it really doing falling or rising?

morrie said:

wookiemeister said:

if we are still talking your motor output signal

wouldn’t that be fairly clean – assuming its being done electronically?

It is an encoder signal. I think it is relatively clean. The VFD accepts it without any problems. I haven’t put my Picoscope onto it.

ah that’s right – you want to tap in from the signal producer and the VFD its talking to (I think)

from what I remember VFDs are connected with cables that are shielded for noise

you don’t want noise triggering the motor

wookiemeister said:

it might say lets look at it over 50 millis()

whats going on with the wave , whats it really doing falling or rising?

nfi. It is simply called as a function.

wookiemeister said:

from what I remember VFDs are connected with cables that are shielded for noise

you don’t want noise triggering the motor

The VFD simply produces a 3 phase frequency controlled output from the 50Hz 240 volt supply. No data exchange involved. It is feed forward.
The encoder signal is from another device that is driven by the motor. It sends a set of step waves back to the VFD via shielded data lines. This makes the VFD feedback controlled instead of feed forward.

morrie said:

wookiemeister said:

it might say lets look at it over 50 millis()

whats going on with the wave , whats it really doing falling or rising?

nfi. It is simply called as a function.

http://arduino.cc/en/Tutorial/Debounce

morrie said:

wookiemeister said:

from what I remember VFDs are connected with cables that are shielded for noise

you don’t want noise triggering the motor

The VFD simply produces a 3 phase frequency controlled output from the 50Hz 240 volt supply. No data exchange involved. It is feed forward.
The encoder signal is from another device that is driven by the motor. It sends a set of step waves back to the VFD via shielded data lines. This makes the VFD feedback controlled instead of feed forward.

suppose a lot of them must work like that – makes sense to control the thing based on what its doing not purely what it thinks its telling the motor to do

wookiemeister said:

morrie said:

wookiemeister said:

from what I remember VFDs are connected with cables that are shielded for noise

you don’t want noise triggering the motor

The VFD simply produces a 3 phase frequency controlled output from the 50Hz 240 volt supply. No data exchange involved. It is feed forward.
The encoder signal is from another device that is driven by the motor. It sends a set of step waves back to the VFD via shielded data lines. This makes the VFD feedback controlled instead of feed forward.

suppose a lot of them must work like that – makes sense to control the thing based on what its doing not purely what it thinks its telling the motor to do

I hadn’t realised that this was possible until I needed it and went looking. I had to buy a small plug in board for the VFD and then set all the parameters via a bitch of a 2 button system and instructions in English written by Koreans.

wookiemeister said:

morrie said:

wookiemeister said:

from what I remember VFDs are connected with cables that are shielded for noise

you don’t want noise triggering the motor

The VFD simply produces a 3 phase frequency controlled output from the 50Hz 240 volt supply. No data exchange involved. It is feed forward.
The encoder signal is from another device that is driven by the motor. It sends a set of step waves back to the VFD via shielded data lines. This makes the VFD feedback controlled instead of feed forward.

suppose a lot of them must work like that – makes sense to control the thing based on what its doing not purely what it thinks its telling the motor to do

The first is known as ‘sensorless drive’, and terms like ‘sensorless vector drive and such get bandied around. It works quite well when the motor parameters are known and can be inputed into the VFD and then even fine tuned by people who know the systems well. So works very well with large systems where the motors parameters are fairly well defined.

Saying all that, anything with some feedback normally works better :)

sibeen said:

wookiemeister said:

morrie said:

The VFD simply produces a 3 phase frequency controlled output from the 50Hz 240 volt supply. No data exchange involved. It is feed forward.
The encoder signal is from another device that is driven by the motor. It sends a set of step waves back to the VFD via shielded data lines. This makes the VFD feedback controlled instead of feed forward.

suppose a lot of them must work like that – makes sense to control the thing based on what its doing not purely what it thinks its telling the motor to do

The first is known as ‘sensorless drive’, and terms like ‘sensorless vector drive and such get bandied around. It works quite well when the motor parameters are known and can be inputed into the VFD and then even fine tuned by people who know the systems well. So works very well with large systems where the motors parameters are fairly well defined.

Saying all that, anything with some feedback normally works better :)

Usually, we set the speeds up with a tachometer at the beginning of a test. In this case however, the loads were varying much more than usual and the speeds were varying with load so much that it was becoming a real issue. Even without tuning the control parameters, the feedback speed control works like a dream. The whole system response is quite changed. It winds slowly up to speed, maintains it beautifully and stops instantaneously now. Before, it was quick to reach speed and took some time to stop.