Acc-24E2 Limit and Flag Wiring - Horribly Ambiguous

[mshaver]

There is a post from 2009 on this topic:

http://forums.deltatau.com/showthread.php?tid=98&highlight=resistor+packshttp://

 

that apparently was never answered by the Delta Tau Insiders.

 

The following excerpt from the Acc-24E2 user manual is very ambiguous and confusing.

"The 4.7K resistor packs used will allow 12-24V

flag inputs. If 0-5V flags are used, then a 1KΩ resistor pack (RP) can be placed in either RP45 or RP46 (refer to the Resistor Pack Configuration section of this manual). If these resistor packs are not added, all flags (±Limits, Home, User, and amplifier fault) will be referenced from 0-5V."

 

This same text has existed in the Acc-24E2 manuals since at least 2000.

 

Delta Tau Guys. I can't find an update or clarification of this on line. Doncha think 5 years is a long time to go without clarifying the original post? Please provide a clear concise explanation of how to set these resistor packs for either 5 volts or 12 to 24 volt operation.

[steve.milici]

The confusing wording will be changed on the next update. The last sentence should read:

"If these resistor packs are not added, all flags (Limits, Home, User, and amplifier fault) will be referenced from 12-24V."

[curtwilson]

Instructions:

 

For 12-24V flag input levels, do not install the resistor packs (default configuration).

For 5V flag input levels, install the 1kohm resistor packs.

 

Background:

 

The ON current through the LED in the optocoupler should be in the range of about 4-12mA. A single configuration of current-limiting resistors cannot handle the full range of input voltages of 5-24V, especially since the 24V supplies are often unregulated and can be up to 28V.

 

The default configuration has 2 4.7kohm resistors in parallel for a resistance of 2.35K. With a 1V drop across the LED, this results in an ON current of 4.7mA at 12V and 9.8mA at 24V (but less than 2mA at 5V).

 

Adding the 1kohm resistor in parallel with these lowers the net resistance to 700 ohms. At 5V, this gives an ON current of 5.7mA (but a too high current of 34mA at 24V).