DIY Controller Question

richard

I came across these (PDF) the other day. Not sure whom the international suppliers are. Try googling the part number.

CothermanDistilling

@GD50 said: I have bought BMS , DDC Bravo Controller ( typically a building management system ) and am thinking of using it to control my still. Plenty of AI DI inputs and also analogue and relay outputs. Dead easy to input rtd's other probes as well as 4 to 20 Ma sensors and also easy to control relay outputs. All the AO's are 0 to 10 v dc. Being more electrical and refrigeration I am at a loss to figure why most SSR are 4 to 32 v dc input voltage and the significance of this range of control voltage.

Carlo Gavazzi do make a range of SSR with a 0 to 10 vdc control input but they are really expensive. Anyone have a way to change a 0 to 10 output to control a much cheaper 4 to 32 v SSR but as said what is the logic of 4 to 32 v control in the first place. CothermanDistilling grim

3-32v is a range of voltages where the SSR turns fully on.... it is NOT variable like 0/2-10V or 4-20ma are... that is why you are seeing the 0-10v being so expensive.

Inexpensive 3-32V SSR's are commonly controlled with a pwm input signal to get 0-100% power. if you put in a square wave of 5VDC that is .2seconds on and .8 seconds off, you get 20% power...

I am pretty sure that someone makes a compatible building management controller for converting the analog0/2-10vdc to 4-20ma PWM. (*note that if you have a 4-20mA source, you can make it 2-10V with a 500 ohm resistor.. and vise-versa)

also @grim had a "big honkin' power controller" that was 4-20mA a while back that was dirt cheap..

richard

I think @grim had a Watson Marlowe ??? unit.

Mine also 4-20mA control is still to built into a panel, has prompted me to think about Atex requrements for my 18KW elements.

For example because the controller buids up heat, the majority of panel builders from what I see (and I may be wrong in this) tend to use individual line SSR's and also assembled with the cooling fins external to the closed panel.

Now with my 30A unit and because of its construction, I can not do this and have to assemble all within the panel.

So I will have to deal with heat build and am curious how others handle this heat build up.

It is my intention to have the panel mounted approx +6m away from the kettle.

grim

There are no longer any sweet deals on the Watlow Power Series Controllers, unfortunately.

GD50

@ClothermanDistilling . i was completely wrong there then as i just assumed that 3 to 32v control was a linear voltage thing ie 17 volt supplied = half output. Never even considered it was a PWM type of thing. Thanks . I will just have to pay for more expensive controls as i am not smart enough electronically to get fancy.

DeltaArtisan

@grim and @dad, Did you ever get your watlow controllers wired up and working? I am looking at wiring up a 480V system and was wondering if that watlow controller was a good path to go down or should look for a different type of controller setup.

CothermanDistilling

@GD50 said: ClothermanDistilling . i was completely wrong there then as i just assumed that 3 to 32v control was a linear voltage thing ie 17 volt supplied = half output. Never even considered it was a PWM type of thing. Thanks . I will just have to pay for more expensive controls as i am not smart enough electronically to get fancy.

Glad you understand.. I am confident that you can find a good deal on some sort of controller that takes in 0-10v (or 4-20ma) and eitehr makes PWM or is the SSR itself.

eBay separate module(there are more robust versions, but can't beat this for $7.25 to test!):

Voltage to PWM 0-5V 0-10V to PWM 0-100% Linear Conversion Transmitter Module @ eBay

Watlow smaller series - maybe set up an eBay search for watlow dc10-24s5 (some are non-analog control)

Watlow SCR Power Controller Delivers Up to 80 Amperes in a Compact Package (PDF)

Watlow power series (smallest is 80-100A, but all seem to be analog control capable)

Watlow POWER SERIES Controllers Provide Microprocessor-Based SCR Power Control Designed for Application Flexibility (PDF)

grim

I only test fired the Watlow with elements in a water bath, but it works just fine. I got something going with Larry on a gin rig that it's going to be used on, but just trying to make some extra money to pay for it. :)

grim

Just remember there is a ton of variation on the Watlow units and you MUST DECODE THE FULL PRODUCT NUMBER.

The ones we were playing with were the 3 zone single phase. If you get a 3 phase unit, it's going to need to be hooked up to a 3 phase element of the right configuration. Since most of us are using single phase heaters, this is the easiest to use for us. Also, you can just use 1 zone if you'd like, and the only issue with the high top-end amperage, is that the wiring lugs are HUGE, like Jumper Cable huge.

CothermanDistilling

YEP - definitely look at the links I gave to figure out what one does you found for cheap before buying...

GD50

Thanks CothermanDistilling. I have gone to a 32 input 24 output bachnet / modbus programmable controller and a 12 input pt100 input expansion module. As yet I am only using for monitoring and alarms as a 0 to 10 vdc watlow controller is a bit rich. Water regulating valves 0 to 10 v modulating are not that expensive either so they are next. More for education and a twisted sense of fun. Monitoring and trend logs are good on the computer though and by themselves make it worthwhile Especially these days as a small controller can be bought for $125 and temp probes for say $5 - American designed and made by Americans in China. Actually he might be Canadian not sure.

It's a weird world we live in at the moment.

dad

I got the Watlow to work in proportional mode, by using a $10usd signal generator.

They are quit over built, but seemed hard to setup. If you can't get them cheaply the Auber setup is easier and cheaper.