JAZZ WITH AC INPUTS

[Kikis]

Hi Guys,

 

I was recently working on a small project to replace a Zelio programmable relay with a Jazz PLC. 

Zelio's power supply and inputs were 230VAC, so i had to install a 24VDC power supply to feed the Jazz and the inputs (limit switches, push buttons, etc.)

In addition, i had to replace two 230VAC magnetic sensors attached on a pneumatic cylinder with 24VDC sensors.

 

I was thinking that It would be great if we had some JAZZ models available with AC power supply and inputs (100-240V).

[Isakovic]

"Jazz generation 3"

I don't know if Unitronics plans this, but there are applications where having 230V voltage for logic is convenient.

[John_R]

9 hours ago, Isakovic said:

I don't know if Unitronics plans this, but there are applications where having 230V voltage for logic is convenient.

Or 120V for us folks here in the US

[Kikis]

There is equipment and machinery powered by 3 phase -3 wire 415V (Neutral is not used), such as industrial water chillers and air compressors.

Manufacturers usually use a transformer to get 230V secondary output and use it as the control system's voltage.

 

Sometimes is not straightforward to switch from an existing 230VAC control system to a 24VDC PLC unit, it requires a lot of wiring changes and extra cost.

 

[kratmel]

I found some soft starters with universal isolated input.
It has wide range of input signals approx 24-250VDC or 24-440VAC.

Inside for all input  - installed high voltage (800V) MOSFET, zenner, 1smd transistor and 6 smd resistors for driving optocoupler.

I tryed to use different signals - it works.
It was good solution - build isolated "HV board" or module  for  Jazz or another OPLC.

But it is question  to unitronics team.

 

[Joe Tauser]

This is a good topic for discussion.

It's not a matter of technology, it's a matter of money.  Approval Agency money.

Specifically - in the US anything that is taken seriously must have a UL listing.  The testing procedure cost jumps up significantly when you go above 50V.  I have a customer that spent $30K to get a modification to a  standard temperature controller UL listed.  He was using a couple thousand a year so he could justify it.

So-

If Unitronics has an AC input Jazz PLC, how many would you buy?  Most new products in any manufacturer's line are driven by an OEM request of a couple of thousand pieces.

All the 24V switching power supplies I sell these days have a 90-264 VAC input voltage range.  Most are less than $100 US.  In the US a standard power supply is 480V, which is easy enough to step down to 120V as JohnR mentioned.  You don't need more than 250 VA to power the PLC and the sensors with some 120V left over to drive contactors and solenoids.

Considering that the control voltage is often routed outside the enclosure, which would you rather grab onto if a cable gets broken or worn?

Joe T.

 

[kratmel]

You are right Joe.

Develop and implement some kind of new device is difficult.
However, in my opinion, some manufacturers have universal discrete inputs with a large range of voltages. Others hold only the standard + 24V.

Jazz - in my opinion - is the  best in old systems that are being upgraded.
 

In some systems there is a problem with different standards of control voltage.
I met American steam washers!!!! with voltage in control circuits 120V. It was strange for me.

1 hour ago, Joe Tauser said:

Considering that the control voltage is often routed outside the enclosure, which would you rather grab onto if a cable gets broken or worn?

It is difficult to upgrade this washer with PLC - we have a standard 220(380)V or + 24V.
At the same time, almost new (2014) crank press for some reason uses 24 VAC and does not have a PLC.

I had a problem - how to automate the stamps on it using a standard 24 VDC PLC.

[Joe Tauser]

Squirrel!

Here's a good article on why the US uses 120V while other countries use something in the range of 220 - 240V-

http://thednetworks.com/2012/06/10/why-does-ukusa-use-110120v-and-others-use-220240v/

Like so many other standards, it's not based on good engineering but rather on historical events, people, and companies in positions of control.  The US standard 120V dates back to what Thomas Edison used.  Other countries are all over the board with 220V, 230V, and 240V at 50 or 60 Hz.

https://www.electronicproducts.com/Power_Products/Power_and_Control/Why_doesn_t_the_US_use_220V_like_everyone_else_in_the_world.aspx

 

Anyway, I feel your pain on interfacing a 24 VDC system to an old AC system.  My solution has been to use a rail full of 6mm terminal block relays with AC coils for the inputs and 24V coils providing contact closures for the outputs.  I almost never use units with relay outputs - if one fails from a field short you have replace the whole PLC or module.  If you don't have room in the original machine you just have to tack a small external box on for the relays.

Joe T.  

[kratmel]

Thanks Joe.

37 minutes ago, Joe Tauser said:

My solution has been to use a rail full of 6mm terminal block relays with AC coils for the inputs and 24V coils providing contact closures for the outputs.  I almost never use units with relay outputs - if one fails from a field short you have replace the whole PLC or module.

This is literally what I used during the upgrade.

However, with transistor solid-state outputs, everything is not smooth.
Usually they are not stable in case of short circuit, although manufacturers write that there is protection. Usually when one of the outputs fails, the multichannel circuit failure and the consequences for the PLC are worse than in the case of a relay, which can usually be replaced even in field conditions.

Therefore, in slow processes - I apply relay outputs with additional intermediate relays (+ an additional diode in parallel). And the outputs I try to offer more than necessary for the process (it is possible to rearrange the program to another output) or in the extreme case, solder the relay from the free channel ..
For high speeds there is no alternative to solid-state outputs.

However, regarding the discrete inputs, I really like the solutions that by definition are more stable - have a wide range of voltages and galvanic isolation.
During problems with cables, they can withstand high voltage (220-400V) and are not damaged. The  relay input  in this case is definitely burning.

I draw the circuit and collect as works of art in the design of electronics.?

 

 

[Cara Bereck Levy]

8 hours ago, Joe Tauser said:

Like so many other standards, it's not based on good engineering but rather on historical events, people, and companies in positions of control.  T

Feet  inches pounds ounces stones leagues...cubits!!!!
and much much more....
 

Interesting articles - I liked the map in the second one, very handy for locating who uses what where.

[Kikis]

There is no doubt that it's a matter of sales and money.

 

Since all major manufacturers of "smart programmable relays" or mini PLC's have 100-230VAC models available (Schneider Zelio, Omron Zen, Siemens Logo), i suppose that there is true demand for small controllers with such specs.

[Flex727]

On 10/6/2018 at 6:51 PM, Joe Tauser said:

Like so many other standards, it's not based on good engineering but rather on historical events, people, and companies in positions of control. 

https://aviationhumor.net/the-us-standard-railroad-gauge-is-4-feet-8-5-inches/