supervisory system for 30 UDC 3000


Thread Starter


i have a question i have to do a supervisory system for 30 UDC 3000, see the problem is that in the manual says that the Rs485/422 link is limited to 16 controller for a host computer, so if i want to use 2 cables for the 30 UDC can i conect to the same computer? do i have to use diferent ports? or only one?

-Another question that i have is what software do you recomend for making the network between the UDC 3000 and the PC? i was thinking visual basic with or labview but im looking another alternatives

- i check the controller UDC 3000 and the Com indicates Rs 422, DMCS and NONE, this means that i can't use the Modbus RTU protocol right?

-final question i seen some program that work as OPC server but i think that in this case won't be necesary because im comunicating only with UDC controllers

i would appreciate all the help that you could give me, because im doing my internships so i don't have experience with this

regarts Tomás
Knowing exactly which model you have is very important. The paper labels on the UDC metal case will provide a model number that any distributor can decode for you.

The UDC 3000 came out in about 1987, and it had light blue plastic bezel with membrane key switches. The membrane key switches didn't hold up to the ball point pens operators used, so the keypad & bezel were changed to the dark gray and rubberized overlay in the 1994(?) era. I seriously doubt that 30 of those are still running, but who knows?

The 3000 was replaced by the UDC 3300, also with dark gray bezel and rubberized front panel keys. The 3300 ran through 2005-6 or thereabouts being replaced by the UDC 3500.

As I recall, the UDC 3000 had only ASCII or DMCS. DMCS was a proprietary protocol, I never saw any documentation on it. The DMCS protocol is obsolete and not supported any more. ASCII was an open, published protocol, but someone had to write a driver for it. It was NOT Modbus ASCII. There was a 140 page manual for the ASCII protocol. It also used the RS-485 port on the UDC.

Modbus RTU over RS-485 came out with the UDC 3300. Modbus RTU is/was an option, it was not standard. There were numerous PROM based, firmware upgrade versions for Modbus RTU. Although the wiring has terminals for 4 wire, full duplex Honeywell always advised running 2 wire half duplex.

Do your controllers have the serial hardware? The manual covers all models, whether the hardware is installed or not, in any given controller.

So in answer to your question, if you actually have UDC 3000s, no, you cannot use Modbus RTU.

If your model controllers do have Modbus, Honeywell offers an inexpensive Windows based HMI called Specview that is designed to work with a basic number of UDCs. It even displays a fairly accurate UDC faceplate.

In answer to your question about the number of controllers on RS-485, if the number is exceeded, you would have to use a 2nd RS-485 port on the PC which talks to controllers 17-30.

An OPC server doesn't buy you anything unless you already have an HMI that is an OPC client.

Hi there,

I did my program in Visual Basic but now when I send data I get no response from the controller. I tested my program and it sends and receives data, so I don't know what I'm doing wrong. The configuration that I'm using is this:

half duplex, 9600 baud, shed time 30, tx delay 1

The UDC 3000 has to be in a a state to be able to send a request? Or is there another thing that I'm not doing? I need help.

Tomás Estrada

Issac Issachar

Why do you think that your UDC has Modbus capability? Does the UDC setup show you 'Modbus' as a selection, as opposed to DMCS or ASCII?

Half duplex:
Did you jumper Tx+ to Rx+?
Tx(-) to Rx (-)?

Which register is your master asking for?

What command are you using to ask for the register?

Have you swapped + and (-) leads?

What error does your Modbus master display?

Hi there Isaac

I was able to finally comunnicate with the UDC 3000 using RS 485, and they don't suppot MODBUS, but I already solved the problem and now it is working fine (it was some mistake with the wiring, that was all).

Thanks for your help.

Tomas Estrada

Glad to hear you found the problem.

Do you still face a limitation on the number of units on the link? I can recall if whether the number of ASCII units was limited or not.

Hi Issac,
and yes when i connect more than 13-14 UDC together i have problem with the comunication, so im going to put 10, 10 and 8 and.(Although im not using the 120 resistor that they suggested,is that a must?, it's works fine without the resistor under 12 UDC, so i don't know if that's the problem)

And i have a problem right now, according to the manual of the UDC 3000 i can change the Local set point using the computer, code 39 , data type 18 and then the value something like this:

03,0204,65,18,39,200,\13\10 (being the 200 the new value) but when i send this data the UDC responds with "invalid data and abort the comunication" , i don't get it why? , i try using the computer set point and works just fine, i look at the UDC and it is selected to work with local set point 1 so i don't see where is the problem, could be possible that the manual it is wrong with that code? or the UDC needs to be in a specific state so i can change the local set point?, because the problem with the computer set point is that when i use it i can't change that set point with the keyboard of the UDC only with the computer and that is a Disadvantage of that SP

Tomás Estrada

<p>&gt; Although I'm not using the 120 ohm resistor that they suggested, is that a must? <

<p>It's empirical, meaning you use it if you need it. The only way to know is to test with it.

<p>Problem with writing setpoint:
My UDC 2300 ASCII COM manual (later model) states:
Note 1. Floating point values may look like this:


They must have four characters and one decimal point as shown, negative sign as an extra character.
<p>Your SP value 200 does not meet the criterion for four characters. However, the manual is not for UDC 3000, but later version UDC 2500. What does your UDC 3000 ASCII comm manual state for data format?

<p>&gt;03,0204,65,18,39,200,\13\10 (being the
200 the new value)

hi Issac , yes last week reading the manual i realize that and solve the problem thanks for the help, now my program it's working

regards Tomás