Bosch proportional valve amplifier

[TF and the wire]

Been trying to find a decent datasheet on the internet to no avail. I am dealing with a Bosch type 2M2.5-RGC2. It's used to control the speed of a conveyor driven by a hydraulic motor. It has a variable voltage from a pot to terminal 2. What appears to be an enable signal to terminal 4. A 24v supply and the solenoid connections from 10 and 11. Can anyone explain the setting of the zero and dither pot. Also the type of output, does it operate the solenoid with varying current rather than voltage? Any links to a decent website would be appreciated.

 

[netblindpaul]

Is that the only info you have on the unit?

What is the detail on the valve?

(Ex-Bosch Rexroth Engineer)

 

[TF and the wire]

The amplifier also has the number 0811 405 106

not sure about the valve and solenoid. Only know it works on 2 wires. I can try and get details tomorrow if it helps.

 

[netblindpaul]

It is a proportional controller, what are you looking to do/for?

 

[TF and the wire]

It's used to control a conveyor that feeds cardboard sheets into a machine. I discovered that it had been causing problems for the operators for a while with it creeping when it is supposed to be stationary. Other electricians have been playing around with it, twiddling pots etc and it is no better. I have only had a quick look at it but found that when stationary, the coil was passing almost 1 amp. I turned the zero pot down to reduce it to around 0.6A and it no longer creeps. I would like to set it up from scratch.

 

[netblindpaul]

OK, then you need the valve data & the command data info.

It also depends on how much "setting up from scratch" you want to do, are you talking about setting the PID loops also?

 

[TF and the wire]

Theres no feedback from the valve. I would like to know what the dither pot does and how to set the zero pot, if it can be done any differently to how I did it. The only other pots are gain, ramp up and down which are self explanitary. Any other info would be welcome.

 

[netblindpaul]

TF,
It has taken me days to find this thread!

The zero pot is to set the null position of the valve IIRC, which without valve feedback is VERY difficult, you will have to do it "live" on the conveyor, you could try it for zero output voltage, but that may not work depending on the valve characteristics, it nulls out the op amps, but, you need to ensure that it is set in the correct manner, never done one of these actual unitsTBH.
However, it is to set the level of the command voltage that the valve will basically be "ignored by the valve"

The dither pot is to restrict the response to "noise" down the signal lines, remembering that we are talking about very small signal values.

Both of these depend on the valve, its response, and the response of the whole system so this needs to be fully understood, including command values & level changes, step responses etc, before these are set up.

 

[TF and the wire]

I've only managed to get on the machine while it is running or for a few minutes during order changes so I have been reluctant to make any major changes. If you go back to one of my earlier postings, you'll see that the main issue was the conveyor creeping when it should have been at a standstill. The Valve was taking almost 1amp. Reducing the zero pot reduces it to around 0.6A at which the drag of the conveyor must be enough to render it stationary. The operators seem happy with it now. Thanks for all the information.

 

[netblindpaul]

The current drawn by the valve is not "necessarily" directly proportional to the valve position, and thus the conveyor speed.
There are a LOT of other dependencies in this control loop.