View Full Version : Newbe needs some last minute help!!!
First, let me extend my thanks to all of you on this forum....using the information available here, I have been able to build my Grinch, SSRs, transmitter, and have had my own little 16 channel show going for the past several weeks....
I had the "bright" idea of adding some additional channels last weekend, and ran into this problem:
Although channels 1-16 work flawlessly on my Grinch, all of the remaining channels are stuck always on....when I tested the board, I tested for on, so it could have been this way from day one....All 64 channels show a signal on my tester.
When I test channels in Vixen, all channels go on, but when I turn the test off, channels 17-64 remain in an "on" state.
Power is coming from PC power supply, dropped to 4.6volts by using IN4001 diodes..I am using the original chips (unable to get Allegro chips in time). I tried bumping power down one more notch to 4.5 v, and had a dead board.
I have tested and re-tested the schematics, and have (or don't have) continuity everywhere that I should...
I don't think that the cable is an issue, as it works for ch 1-16, and when unplugged, all lights go off...
If any of you can get a few minutes away from your displays at this late date, I would appreciate any help that you might be able to offer (or at least a better place to start)
12-18-2007, 08:49 PM
did you try a little more volts like 4.7 and see if that helped? even a reboot on the pc might fix it.
are we talking the lights on the 595, or the lights on the relay? or both?
If both, try changing your parallel port mode in bios, try them all to see which is better.
12-18-2007, 09:41 PM
Just because you didn't say..... Did you remember to set the plug in? Double check them.
I am using the Olsen 595 Plugin and have it set channels 1-32...tried it setup from 1-64 to see if I just had a bad chip...(I tried swapping out the controller chip as well, with no success)
The lights are being pushed on from the Grinch...I checked it with a tester and was showing signal being sent on all channels...if I unplug the control cable from the SSR, the lights go off.
I had to step down the voltage to 4.6 v to get it to work....when I was initially testing, I got it to work at around 4.75 volts, but had to bring it down to 4.6 to get it to work with any consistency.
I have not tried changing the Parallel port mode in BIOS....I'll give that a shot and see if that makes a difference...
I'll try it on a different machine as well to see if that makes a difference....I was not really thinking so much about problems on the control side of things....
12-19-2007, 10:45 AM
Try swapping chip#1 and chip#2 and see what happens.
12-19-2007, 06:09 PM
OK firstly when you are adjusting the board, lets see if you know why. From vixen do an ALL ON and measure the signal foltage from the parallel port - ideally that will be 5V, but in most instances that is roughly 4V, so thats why we add a 0.6 or 1.2V drop with 1 or 2 diodes.
You said " dropped to 4.6volts by using IN4001 diodes". Each diode drops the voltage 0.6 volts, so unless that power supply was running pretty high, you may have made an error in the number of diodes you added.
The chips will turn on at roughly 80% of the rated voltage, and off at 20% (Genberal rule of thumb). We reduce the voltage because if your parallel port puts out 4V, which is 80% of 5V, it will USUALLY turn the chips on, but not always. Reducing the inpit voltage to 4.4V with a single IN4001 or 4004 diode (I use IN4004 as they have a 4A rating, rather than 1A of the 4001's) means that that 4V is now over 90% of the input voltage, thus will always be detected as a high. Many chips have a dead band in the middle, so you really want to keep your input voltages away from that area
Change the parallel mode as mentioned, but since its working with the first 16 chans then I doubt it will be that, but you never know.
Just check that you have not made a solder bridge somewhere between the output of the last IC thats working and the first one that has the issue. It sounds like the clock signal is getting through but the signal has been tied high by eithor the chip or an error on your board. Carefully check that track and pins on each IC for any sign of a bridge
You guys are AWESOME!!!!
I was indeed suffering a voltage drop on the clock signal between ICs 1 and 2...I could not find the problem, so I soldered on a new jumper direct to the pin 3 socket, and was back up and running, 32 channels strong now!!!
Thank you so much for all of your help....I know that I would have not thought of checking the clock signal voltage like that,....
12-20-2007, 04:39 PM
glad to hear its working again :)
Thanks again to all for their help...to see what you helped me accomplish, check out the video...(I know that there is a separate area for the show links, but this is a follow up to the assist posts....It's not worthy of "showing off" yet....just wait until next year!)
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