square wave fucntion generator . help

[neurofen]

I might have been a bit hasty. i bought a function generator kit which outputs a square wave , the frequency can be changed with a pot.

I wanted to use it to test and control my stepper motors if the pc's turned off.(just back and forwards at different speeds)

It's got a 0-5v phono output socket.

Any ideas how i wire it up to one of my gecko g201's? They need step/direction/ and a common ground input..and theres only the square wave ouput of the generator.


im stuck, thanks in advance

[Al_The_Man]

You will have a common and signal output, this will go to the step input and respective common on the Gecko, for the direction use a separate on/off switch to either switch to ground or 5v.
If the Gecko is active high when open circuit, then you just need a switch to common.
Al.

[neurofen]

thanks al, can i do away with the direction (and teh switches) and just wire to common and step? or does the circuit need the third route

otherwise.. when you say switch to ground(do you mean earth - ground )


edited

[Al_The_Man]

Should work, try it!
Al.

[neurofen]

will it destroy the driver if i get the common and signal around the wrong way

[Al_The_Man]

Originally Posted by neurofen otherwise.. when you say switch to ground(do you mean earth - ground ) edited

Actually I did not mention ground, I prefer to use common which is often substituted for it but can cause confusion if there are Several different 'Grounds'
If the Gecko uses 'ground' then this is what they mean by common.
NOT necessarily Earth Ground, See what I mean!
Al..

[Al_The_Man]

Originally Posted by neurofen will it destroy the driver if i get the common and signal around the wrong way

You should not if only using the two signals, but your board appears to have a RCA or audio jack type output?
The centre would be the signal and the outer the common.
Al.

[john_100]

Hi Neurofen ,

having found the function generator circuit here -
http://www.maplin.co.uk/Media/PDFs/N42FL.pdf

depending on the load on the +5v regulator
you may be able to supply the +5v to the G201 dir and step opto isolator common +5v i/p

connect the phono screen / function gen negative supply via on /off switch
to the - direction input on the G201
to change direction
http://www.geckodrive.com/upload/G201-REV-16-MANUAL.pdf


and the phono centre pin to the G201 - step input

I would power the function generator from the minimum supply possible
approx 7Volts or so
just in case the opamp fails , as it is supplied directly from the DC in to the board
and not the 5v supply to microcontroller IC
( you don't want to connect 12v to the 5v in on the opto isolators )

plan B is to build the Gecko's test circuit

http://www.geckodrive.com/upload/STPDIRTester.pdf

John

ps if the LM 358 in the function gen. can not sink the current from the G201
you can add a npn transister and 4.7 to 10K resistor to buffer the ic

[neurofen]

right here goes then, just need a few mins to heat up the soldering iron to disconnect the second end of the phono cable...

any ideas if the gecko will power up with only 12v? its rated 24-80VDC

[john_100]

following the link I found you need a mimimum of 18V for the G201

to test the drive from the function generator
try a led and 300 -500 ohm resistor
see if at 1 or 2 Hz the LED blinks

Gecko input circuit http://www.geckodrive.com/upload/OPTO%20INTERFACE.GIF

John

[Al_The_Man]

They say 18vdc min, but I thought the idea was to test your Steppers? you will need to supply the recommended voltage for them to operate correctly?
Al.

[neurofen]

thnaks both of you for the input, tried both ways but still no movement from the motors yet, probably because as you say theres not enough juice,
. i was trying to power from one of the pcs 12v molex connectors .

i tried a 5v line to the optio circuit in the gecko from the pc instead of from the generators input(no croc clips)..

i will try again when the main psu is up and running. i should give it a go now really, but the plan is to not power it up until its secured somewhere. those caps are nasty and i'd more than likely electrocute myself..
is tehre a quick safe way of discharging caps?

i'll take a look at the gecko test circuit in the morning, thanks for the link, but al's right i need to power th emotors as well as the driver.