McCready00
Active Member
Make a DMX tester.
I made it and it seems to work well..
Anyone made it and have any comments on it?
I made it and it seems to work well..
Anyone made it and have any comments on it?
Homemade DMX Tester
- Thread starterMcCready00
- Start date
Congratulations, McCready00. I'd like to think you found the link to those instructions in our Collaborative Article: http://www.controlbooth.com/forums/...cles:DIY+DMX:+Demux,+Protocol+Converters,+etc.
Send me one when you're done.
Probably (but depends on your scroller or other gadget) it would be pins 2&3, see http://www.controlbooth.com/forums/lighting/7714-color-scrollers.html#post90957. As long as you're building one, consider another LED of a different color or style, to verify voltage between pins 1&4. Do not use on Morpheus ColorFaders.
Send me one when you're done.
McCready00
Active Member
here's the one I've done last week.
That looks brilliant!
I haven't read this specific article, but I remember in some othe guide, someone said to put 2 LED's in pararell, but reversed, and of a different color, that way you can see if the "data" is actually changing.
Did the LED fit in the hole that well naturally, or did it take some knifing/force?
I haven't read this specific article, but I remember in some othe guide, someone said to put 2 LED's in pararell, but reversed, and of a different color, that way you can see if the "data" is actually changing.
Did the LED fit in the hole that well naturally, or did it take some knifing/force?
McCready00
Active Member
A bi color LED is essentially two LEDs in one package. The two LEDs in the package are different colors and polarities, with a common pair of leads.
Keep in mind what this tester can and cannot tell you. It can tell you there is a signal pressent, and possibly that the signal varies. It cannot tell you if the voltage swing is correct, corrupted in some way, or has noise on it. But, this little tool could come in handy.
Keep in mind what this tester can and cannot tell you. It can tell you there is a signal pressent, and possibly that the signal varies. It cannot tell you if the voltage swing is correct, corrupted in some way, or has noise on it. But, this little tool could come in handy.
It will tell you quite a bit, actually. See http://www.dfd.com/pdf/tstrdata.pdf. I'm assuming the DIY model conveys all the same information, but I may be wrong about that.
This is on my list of things to put together. However, while it does tell you if the signal is alive, it doesn't help you with voltage, etc. Has anyone built one of these with test ports to access the signal with a multi-meter? If you pot it, you will need something inserted to ensure access (and hope the resin doesn't seal your path), but it would be a great addition to the tool.
Tim.
Tim.
waynehoskins
Active Member
A scope in a tester could be a real challenge. However, rather than connecting the resistors directly to the connector, it should be pretty simple to insert a couple of binding posts between the connector and the resistor (or LED). This would provide access for any level of testing equipment that you should choose to apply.
Looks like I have a trip to Radio Shack coming.
Tim.
Looks like I have a trip to Radio Shack coming.
Tim.
waynehoskins
Active Member
McCready00
Active Member
Here is what Nick Mobsby wrote inside his book called Practical DMX :
"The value of the resistoris a function of the characteristic impedance of the cable. This is the natural impedance, in Ohms, of an infinite length of the cable. Such a length of cable is defined as being 'free of reflections'. Typical cables used for an installed DMX network, such as Belden 9842, have an impedance of 120 Ohms. Most cable range in impedances between 90 ans 150 Ohms. Values close to the characteristic impedance will also work. For this reason I recommend the use of a termination resistor value of 120 Ohms."
"The value of the resistoris a function of the characteristic impedance of the cable. This is the natural impedance, in Ohms, of an infinite length of the cable. Such a length of cable is defined as being 'free of reflections'. Typical cables used for an installed DMX network, such as Belden 9842, have an impedance of 120 Ohms. Most cable range in impedances between 90 ans 150 Ohms. Values close to the characteristic impedance will also work. For this reason I recommend the use of a termination resistor value of 120 Ohms."
you can buy 5 pin connectors from Digi-Key Corporation - USA Home Page Mouser Electronics - Electronic Component Distributor Altex Computers and Electronics or Home - Ace Electronics
as far as resistors go i use 120 ohm 1% (5% at the most) 1/4 watt. All you are trying to do is terminate the signal, so the only wattage pulled is that of the resistor.
as far as resistors go i use 120 ohm 1% (5% at the most) 1/4 watt. All you are trying to do is terminate the signal, so the only wattage pulled is that of the resistor.
I use seperated leds so I can see if one is not responding which would indicate a driver ic problem. If you use a combined bicolour led it is hard to see seperate activity as one led die is always brighter that the other.
An led has a typical voltage drop of 2.2 volts so if you want to expand on this range of led testers, put a zener diode in series with the led so you know it will not light up untill it exceeds a voltage, so you can see if your scroller supply volts is in range.
An led has a typical voltage drop of 2.2 volts so if you want to expand on this range of led testers, put a zener diode in series with the led so you know it will not light up untill it exceeds a voltage, so you can see if your scroller supply volts is in range.
