About CUTOUCH 1721 series

[hartoksi]

I am looking at the specs of CUTOUCH 1721 series. I could not find any information about max. current information of 24V digital NPN TR outputs. Can you please?

[sci_prez]

I don't have the exact reference at hand, but I believe the outputs are based on a ULN2803A darlington driver. Max current for one channel is 500 mA. Channels may be parallelled for more current.

Cheers,

Tom Sisk

[Mike]

Sorry for the late reply, I wanted to get a definitive answer from our electrical engineers.

Tom is correct. Our electrical engineers sent me the attached datasheet for reference.

[hartoksi]

Does CUBASE-32M and CUBASE-64M have same output format with CUTOUCH? I mean, does CUBASE32M & 64M's outputs have ULN2803?

[Mike]

The 32M and 64M both use the KTC3875S.

[hartoksi]

Thanks for your replies.

As far as I understand we can not use 32M and 64M for controlling selenoids (valve air control). I have checked ours and they need 0.5A approx.

We don't like use relay outputs for life problem.

What would you do if you need to control a load about 1A with your low cost products like 32M?

[Garrett]

The absolute maximum ratings for transistor based devices are not actually limits that you should assume can be safely approached. Nor it is easy to determine exactly what that limit really is.

The problem is compounded by the fact that there are multiple junctions in each device. Heat from one junction will affect the other junctions.

However, the datasheet does have some information that can help. First would be the saturation voltage, Vce. It appears to range between approximately 1 to 2 volts depending on current. You can easily determine the power being dissipated by the junction: say at 200mA and 1V, your dissipated power is 200mW of heat. That heat needs to go somewhere.

Consider the case where all 8 drivers are dissipating 200mW. That's 1.6W total, which needs to get out of the device package. R(theta junction ambient) is listed as 55C/W. Absolute max junction temperature is 125C. So to keep the junction less than 125C, you have to keep the outside case of the ULN2803 less than 37C. This is likely to be difficult under continuous duty, with no heatsinks (the CT1721 does not have heatsinks on the driver chips).

So I would recommend keeping the CT1721C outputs at 100mA or lower, in cases where all outputs in a driver chip may be on at the same time for more than a few seconds. This results in a maximum chip surface temperature of 88C. Without actual case-to-ambient air dissipation data that's also tough to calculate precisely, but in practice the surface temperature does not reach 88C under normal ambient temperatures.

For higher current drive applications, it will be necessary to use an external switch device with more current handling capability. An N-MOSFET can easily be driven from an open-collector output using a pullup resistor, as long as the switching rate is below a few KHz. MOSFETs are available that can handle dozens or hundreds of amps with far less heating than a BJT device.

[hartoksi]

Thank you for your time.

In fact, I am Moacon user as you may see in my older posts. We can use source output modules of Moacon directly to drive selenoid valves in our projects.

On the other hand, to be honest, the cost of projects based on Moacon modules is the problem which forces me to search for alternatives in Comfile product range. In many project we do not need high speed execution time of code and so I thought to use Cubloc series instead of Moacon. The problem is that, we are not deal with 5V TTL levels but 24V levels (Sensors, piston valves, etc). Cubloc core modules are at 5V TTL levels. And ıt seemed me that is not what I want. Then I discovered the baseboard extensions and excited. Inputs of baseboard was at 24V which I need. Outputs was also 24V levels but was not sufficient for our loads about 0.5A. I am suprised of that and fell in doubt that am I only the one who need 0.5A current to drive a simple piston valve which is a generic application. The peoples who use Cubloc series should need such a current and should handle it in a way. That is the thing I want to locate. I believe one of your product is the one I need but the alternatives I have seen in the web site was not until now.

Transistor outputs of baseboard ... Not sufficient current
Relay baords ... avoding to use them beacuse of mechanical contact solutions
SSR8 board .... For AC purposes only
Buinding my own extension board with ULN2803 .... I am not eager to do that beacuse of heavy working hours and days (designing, drawing, board production, mounting, testing etc).
Your instant solution .... ?????? waiting.

PS: CUTOUCH is ok. We can use it where we need HMI based project. But the solution for projects which does not need HMI is still empty.

Regards,

[sci_prez]

You are correct that many of us need to drive loads greater than provided by an on-board driver.

The usual methods are to use relays (which you don't like) or power transistors, either bipolar or MOSFET.

The lowest cost for you may be to use a common IRL520 MOSFET which will easily drive loads much greater than 0.5 A and never overheat. They can be mounted on a simple circuit board or simply incorporated at the terminal blocks of your system. I often mount them on the inside of the system enclosure for additional heatsinking and mechanical protection.

Cheers,

[hartoksi]

Then, Comfile must consider to develop a base board which can drive 1Amper loads (PNP/NPN). That is the a big missing chain in Comfile product range, isn't it?

[sci_prez]

I have sent a private email which describes a possible solution to your controller needs.

Cheers,
Tom Sisk

[RedHunter]

I have a similar problem, but whilst I am happy to use relays I am running my CuTouch 1721 on a 12v DC supply, and need 12v DC outputs to my solenoids. This means that I cannot use the SSR8 boards because I understant they only switch AC and the Relay 8 boards need a minimum of 16.8 v to pull in the relay.
Is there any easy solution other than unsoldering the relays and replacing them with 12v versions?

[sci_prez]

The 1721 has NPN output transistors in a current sinking configuration that will work fine with external 12 volt relays.

One solution would be to build yourself a relay board. Or, several manufacturers (Weidmueller for one) sell multi-relay modules at various voltages. I've used one with 8 relays and it worked well. If space is not too tight, you could also use socket-mounted relays and clip them to a piece of DIN rail.

Another inexpensive route is to use the TTL outputs on the 1721 to drive a logic-level MOSFET which will operate your solenoid.
A IRL520 can switch upwards of 9 A with a 5 volt signal on the gate.

Cheers,

Tom