Need something simpler/smaller than a micro-plc 2

dieselvette · Oct 6, 2006

Does anyone know of a programmable device that I can buy "off-the-shelf" for less than, say $75? I need to replace the Siemens Logo we currently use with something cheaper and/or smaller. Just an open circuit board would be perfect, doesn't need to be DIN rail mount or anything.

Needs to have (digital) 2 inputs/4 outputs, some kind of memory retention, and run on 120VAC. Outputs rated at least 3A/120V each.

Outputs are all simply timer controlled. Inputs are just for a "reset" function and a "pause" function.

I would like to stay away from having to buy my own EEPROM programmer or build my own board from scratch, I'm pretty much looking for something in between designing my own circuit board and buying a micro PLC.

Nic Van Engen
Electrical Technician

ScottyUK · Oct 6, 2006

How about one of the Zelio smart relays from Telemecanique?

http://www.telemecanique.com/en/products/index_fon5_fam10_aut_zeliologic.htm

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Sometimes I only open my mouth to swap feet...

dieselvette · Oct 6, 2006

Thanks for the reply, ScottyUK

I have yet to find a supplier that can get me ANY "smart relay" (Idec, Siemens, Telemecanique, Omron, etc.) for less than $100.

Do you know of any? If I can't get it for, say, $75 then I could just as well stick with what I've got.

I am building a lot of these machines, so saving a few dollars here and there will be significant in the long run.

Nic Van Engen
Electrical Technician

ScottyUK · Oct 6, 2006

Telemecanique's SR2D101FU with 6 digital inputs and 4 relay outputs costs £60 in one-off quantity from RS Components, the UK equivalent of Digikey. That's about $110 US. With a bit of shopping around I'm pretty sure could knock at least 20-30% out of that for a quantity purchase from one of the big wholesalers (Newey & Eyre in the UK, for example).

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Sometimes I only open my mouth to swap feet...

richs · Oct 6, 2006

Hiya-

I don't think that you will find something completely off
the shelf that will do that switching requirements for the
$75.00 price break. Offhand, I would suggest a microplc
with a couple of external relays. Still would have to
get a power supply for the miniplc.

The big problem, sorry to say, is the liability of switching
that voltage/current, along with the UL, FCC, CSA, etc,
etc, etc........

I am working on an open PLC device that requires only one
IC. You can program it serially with a low voltage programmer
(which is not on the site yet), is NOT FCC, UL approved, and doesn't have the kits for it yet.

However, there are "el cheapo" programmers for the pic that do not require anything more than a prototype
lashup for the programming.

My version uses a couple of resistors a transistor and the parallel port from a PC.

It's kludgy and "finiky" so I would suggest doing a google
search for a better one.

OTOH, the plc is a DC version that can run you about $2.00
for the processor, you still need a power supply, and
a couple of transistors for driving the relays and
resistors. If you are building several, then this might
just do the trick. There are wall wart and "power brick" power supplies that will work that can be had for a couple
of bucks.

The link (although not complete) has the documentation and the software. It's all free! I did it to give back to the electronic community. It's alpha code, but seems to
work. Hope to have it on sourceforge soon, but the
temp. link is:

http://getok.net/plc2pic/index.php?next=home

Hope this helps.

Cheers,

Rich S.

itsmoked · Oct 6, 2006

Hi dieselvette.

If you are are going to be using a hundred of them then a custom design might actually work well for you. Often you can also cover all the rest of the functions you need done and add nearly free features, if you go that way.

diesel corvette?!?!? Strange....

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

dieselvette · Oct 6, 2006

Where can I look for a custom design supplier? It seems like a good idea to go custom-made, but it would complicate things a little (longer lead time when I need the product, need to buy in more bulk, etc.).

I see that at flamin systems you build all kinds of stuff - probably a little higher-end than what i'm looking for. Would a company like yours be willing to deal with something like this? Are there companies who are? What kinds of costs are we looking at for prototyping, etc.?

Diesel Chevette - its a long story.

Nic Van Engen
Electrical Technician

dieselvette · Oct 6, 2006

Rich:
It looks like we're on the same page here, trouble is I don't know if I'm willing to dive into the discrete electronics field head-first at this point.

Being UL/CSA/FCC/etc. approved is not a concern at this point, I just want to determine: 1. Is there something that will work? and 2. Is it cost-effective and readily available?

My familiarity with programming is very limited, I've done lot's of work with Siemens & AB/Rockwell PLC's but nothing to intricate or complicated. Anything beyond that would be a learning curve for me.

Nic Van Engen
Electrical Technician

Skogsgurra · Oct 6, 2006

Hi Nic,

There are lots of companies doing that kind of work. I am sure Keith can do it for you and if you google +embedded +consultant and similar combinations, you will probably find a few hundred more.

A real cheap solution would be a simple power supply using either a series resistor, a diode, an electrolytic capacitor and a three-leg linear regulator (have been down to a 400 mW zener in real cost sensitive applications).

A small micro controller can do the work for you and for lowest cost, I would use triacs instead of output relays.

I estimate that the design (a very simple matter) would cost you one or two weeks, including programming the micro and testing the "system" out. Production cost will be somewhere between 20 and 30 USD. Terminals and/or connectors tend to be the costliest part of such a design. The cost is also dependent on what precision you need for timing (internal oscillator is cheap but chrystal is more exact).

UL and/or CE marking may be the toughest and most expensive part of it.

Gunnar Englund

http://www.gke.org