GPO's , PWM and capacitors ....

arr2036 · Post by **arr2036** » Sat May 28, 2005 12:31 pm

I have a 2500 rpm panaflo fan connected to one of the fan headers . At stock the fan is 41DB so i was hopeing to reduce it's speed using pwm .
However when i set different frequencys for the gpo , there is an audible sound from the fan , so even when its running quite slowly you can still here it . I figured the reason for this was that PWM works exclusivly by altering the frequency of the output on the GPO and not the voltage and that it was causing the noise . The solution i came up with was to stick a 1000 mf capacitor across the gpo , but when i powered on the unit it acts really strangly like the unit is power cycling every 1/4 of a second .

So two questions.
Is the rpm management done exclusivly by altering the frequency or is a combination of frequency and voltage.

And secondly , why does the unit cycle with a capacitor connected , it seems very strange . Not really a problem just curious to why it does it

2bigfan · Post by **2bigfan** » Sat May 28, 2005 11:38 pm

hi

im no admin. but the rpm management done exclusivly by altering the frequency. i think

i posted a post (about adding a volt meter) and was told that the output stade the same voltes (12v)

Tom · Post by **Tom** » Mon May 30, 2005 10:35 am

Hi arr2036,

When you are varying the speed of a fan using PWM, you will be varying the pulse width or the time the voltage is being switched on and off. We introduced the frequency command to for auditory/visual purposes. If you have LEDs on the GPO, then you will want to increase the frequency to reduce the flicker. If you want to hook up a small motor to it, you would want to reduce the frequency to about 20Hz to reduce any kind of noise.

Any of the capacitors connected to the GPOs are strictly for decoupling.

I hope this gives you a clearer picture. If you have anymore questions or concerns, please feel free to post.

Best Regards,

arr2036 · Post by **arr2036** » Thu Jun 02, 2005 5:36 am

Ah , ok , yes i found around 19hz works best but there is still a deffinate clicking coming from the fan

. I just wanted to see if i could use a capacitor to smooth out the pulses and convert the output to a steadyish voltage .

I'm having huge problems now though , whatever i do i can no longer alter the power on settings for the GPO's . Sometimes it will let me change them when i connect to the display , but when i turn it off and on again it reverts back to these strange settings where all the GPO's are at different levels with GPO 2 being fully off and the rest being set at quite low levels.

Also now when i have the relay connected to a 240v supply and i power up the unit , it ignores all the power on settings and sticks everything on full ! It then also ignores any attempts to change the GPO outputs , and then when i connect to it using LCDC theres iterferance on the screen with lots of little underscores appearing everywhere . But that only happens when the relay is actually connected to a supply , it can be connected to the unit without and supply and everything will work fine (apart from the GPO's being stuck at strange settings) .

I wouldn't have thought everything would be so sensitive :S . Is there anything you can suggest to fix the Power on issues and the interferance coming from the relay ?
Oh and i'm using a MX412 .

Tom · Post by **Tom** » Thu Jun 02, 2005 9:22 am

Are you using an internal or external USB cable?

arr2036 · Post by **arr2036** » Thu Jun 02, 2005 9:56 am

External as in it has standard usb plugs on each end , i'm running it from my laptop for testing .

It seems the interference problem with the display was a one off as i havn't been able to reproduce it .

However , there is still a deffinate problem with the GPO's and the relay . I set the up button on the display to turn GPO 1 to 100 and the down button on the display to turn GPO 1 to 0 . When i press up the relay turns on like it should , then when i press down it stays on .If i then unplug the relay and plug it back in , it will go off and stay off . It's almost like the GPO is latching on until the relay is physicaly disconnected .

I think i know how to solve this though , i'm going to make up a little transistor buffer and stick it inbetween the GPO and the relay.

The problem with changeing the start up settings is still there , it has also extended to changeing the boot screen or any of the power on defaults such as contrast or back light brightness .

Any suggestions as to how to fix this ?

Tom · Post by **Tom** » Thu Jun 02, 2005 10:26 am

You can change the defaults with uproject. Uproject will be in the ecd that came with your display.

In the uploader tab under other->raw data you can enter the following command.

/254//195//1//255/

Here is a description of each number.

254: Command prefix
195: Set default GPO state command
1: GPO number, this can be changed from 0 to 7
255: The PWM value, which can be set from 0 to 255

Press F9 to execute the command.

You can use these raw commands to do any of the display's functions. All the commands are found in the manual at http://www.matrixorbital.com/files/LK204-24-USB_TM.pdf .

I hope this helps you out with the defaults.

Best Regards,

arr2036 · Post by **arr2036** » Thu Jun 02, 2005 1:03 pm

Hmm it may help but there in no file / folder on my eCD called uproject , the cd version i'm using is 3.1 .

Tom · Post by **Tom** » Thu Jun 02, 2005 1:27 pm

You can also download uproject at our new Matrix Orbital technical support website at http://www.matrixorbital.ca/software/so ... /uproject/ .

Best Regards,

arr2036 · Post by **arr2036** » Thu Jun 02, 2005 3:53 pm

Excellent , i can set the defaults now

Thanks Tom !!

Still very strange with the GPO's latching with the relay, have you heard of anything like this happening before ?

Tom · Post by **Tom** » Thu Jun 02, 2005 4:00 pm

To be perfectly honest, I haven't heard of this issue before. I will be testing some relays with the display in the near future though, so i'll see If I can come up with the same situation.

If you have anymore questions or concerns, please feel free to post.

Best Regards,

arr2036 · Post by **arr2036** » Tue Aug 30, 2005 5:02 pm

Found out what the problem was , i was using a rather large relay and it was causing EMI when opening and closeing , switched to a solid state one and everythings fine

.

However somehow during the process GPO's 5,6,7 went very strange , they now turn themselves off when set to on and on when set to off :|

I was also wondering if you had the raw command to set the PWM frequency

Many thanks,
Arran

Tom · Post by **Tom** » Wed Aug 31, 2005 9:20 am

Hi Arran,

Please refer to this link http://www.lcdforums.com/forums/viewtop ... +frequency

Best Regards,

arr2036 · Post by **arr2036** » Fri Sep 02, 2005 9:16 am

Is there a forth parameter you have to include , because whenever i try and execute the command the text just appears on the display and nothing changes

Tom · Post by **Tom** » Fri Sep 02, 2005 9:41 am

Did you cycle the power after?