Automation. Sometimes simple things just miss us. Looking for advice please.

Discussion in 'The Projects Forum' started by boydage, Oct 7, 2016.

  1. boydage

    Thread Starter New Member

    Oct 7, 2016
    Hi from New Zealand,

    I am slightly into electronics having built 4 CNC machines which the last two are working wonderfully. I am on a new project now but seem to be stumped on what is the best and cheapest solution for what I want to do.

    Having worked in the ROV industry and having also very limited experience in electronics I have so much going on with ideas I am completely missing the point.

    Short story:

    1. I have 10 woodworking machines in my workshop running on 230v.
    2. I want to install a current sensor on each machine which, when turned on will activate a relay to supply 24vdc to a pneumatic solenoid which will then open a gate via a pneumatic miniature cylinder for my extraction system particular to that machine, and also activate a common relay to start the 230v 3hp dust extractor.
    3. When the machine is turned off, the pneumatic ram will spring shut with loss of 24vdc to the solenoid and the extractor will shutdown.

    I seem to be having trouble working out how to convert the small voltage (milli volts) from a non evasive current sensor to enough voltage to operate a relay. It seems so simple yet I am unsure where to start.

    Everything else, the physical gates, pneumatic rams, solenoids, air supply is no problem. Just the sensor to the relay. I was considering a circuit using a transistor with an arduino board but feel that’s over the top.

    What do you think? Would you mind giving me an idea to work on? Warm regards Boyd
  2. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    I had these[full_desc]=Y&s[sku]=Y&s[match]=all&s[cid]=0 in my bag of tricks for you.

    The deal is some require power, some don't and you might have to hunt for something. They all have a maximum and you have to just use one of the wires. It can be wrapped around the sensor multiple times to increase sensitivity (1x, 2x etc) . You can't exceed the maximum current.

    You don't need a current sensor.

    This is something different.

    I/O modules is yet another way.

    In SOME cases you can fit this stuff in the breaker box if all the ducks are in a row so to speak. You typically have one wire you can run the wire through the sensor. You just have to make sure everything else is up to code with mixed low and high voltage wiring. let's just say you have a sub-panel in the shop. You can put everything in a NEMA enclosure and pass it through to the power source.

    DIN rail terminals and devices is the erector set of the control engineer. You add wire raceways etc.

    There could be an odd device that won't fit into the scheme of things.

    Your problem is a little more complex than you imagine. The machine has to open the gate too.

    A single box measuring current is a good start. Now throw a 10 HP 3 phase gizmo and you have to use something else.

    In the US, we have what's called class II wiring. It has to be power limited to 100 W and usually around 24 V or so, so no conduit is required, but you don't want a board to bang into it either. I had to buy a FAP power distribution panel for what I needed to do. I could logically control one of the 8 or 16 outputs.

    Hint: This company: Let's just say, it saves a LOT of work. Only issue i had was operating some strobes because of surge current. They were from the same manufacturer, but a different design. The newer ones had less kick to them. So, you may have an interface to the gate valves. You might want to use air cylinders too. ASCO has some nice manifoldable valves. I just had to clean them first to operate on Argon without an oiler. Air can be a lot easier. You can change the rate they close and open and the valves I used had a manual control on the valve too.

    So, you have two things at this point, A way to activate a valve and a way to monitor if a machine is turned on. 24 VDC is the standard. I used AC maybe because I didn't know any better.

    If your the only one operating the machines that's one thing. The downstream side could also get messy. e.g. a VFD on your vacuum.
    You might need some interlocks of some sort.

    let's add one more detail - the ability to use an RF switched hose. e.g. A hand power tool or a temporary tool or use it when one is broke. I don't know.

    Let's hope you don't need to disable tools when too many are in use?

    NOW what?

    You can't be turning off the vacuum all of the time, so it needs to run longer than the last user. In fact it might run at different times depending on how far away it is. It may need a port that needs to be controlled open (not just on and off). It also might need outside air. Yep, I'm complicating stuff on purpose.

    In simple terms, you want to turn the vac when you use a piece of equipment and open it;s corresponding hose. Not exactly!

    When you turn that equipment off and it's the only one, you have to let it run for a while until person A gets to machine B. Only if he doesn't do that would you want to shut down. You may need velocity control (fan speed) and//or a controllable gate or even a port that goes no where but can be opened partially. A VSD (Variable speed drive cuts noise down and your electric bill).

    Then you can get really fancy and every so often run with everything open and measure the static pressure or measure the current that the motor draws. Save this info and do it every day at some pre-determined time. You can definately determine filter change/clean times and look at the general performance.

    You may even need a way to reverse the system?

    Anyway food for thought.

    it's all over the map and it's meant to be to give you ideas. the one thing you don't want is to keep restarting the dust collector when you move from machine A to B in 30 sec after turning off machine A.

    You do want to know when the dust collector needs maintenence.

    Air cylinders may be more useful. You can have air to open, air to close and spring to open, spring to close etc.

    Synchonous motors work well. In a home system the controller can basically control static pressure by knowing current. and vary the speed of the VFD accordingly. Bypass dampers may not be required, because the motor is doing all of the work. Changing it's speed based on the load.

    System restrictions like a bad filter can be found if all the dampers are open and it characterizes the system daily and looks for a substantial change in static pressure. Actually, that how my home system works. Every day at 1 pm, the furnace runs about a 5 minutes test where it assumes all dampers are open. if it were a zoned system, it would open all zones. You get a notice when to change the filter and when you do change it, you reset it back to 0% of capacity. The filter is changed about every 6 months and may take up to 45 minutes to do so.

    Velocity sensors and dust don't get along. I know. They have to be cleaned. I'll tell you that ones with numbers makes life a LOT easier.
    the air cleaner i use is this one:|3149|aprilaire 5000||S||114735734218&gclid=CNGHtqKGyM8CFUEmhgodzWEJXg The element comes compacted and then the electronic portion has to be cleaned which attracts the smaller stuff. The furnace tells you when it's dirty.

    Let's add one more wrinkle and that is the air supply and exhaust. Had a lab running with 100% make up air

    Thinking cap on. Don't throw any ideas out right away. So...
    What would i like to have if I had all the money and time in the world?
    What must I have
    What do i need?
    What would i like to have?
    What do i need now.

    What you will find is that there are things that could cost you so little money when done in the initial stage. let's just say it's running of wires.
    Running one cable is almost the same as running 5. So, you add the "hooks" for a possible upgrade. Sizing an enclosure might be way big for the initial project, but adding one later will cost tons.

    You may already have air. This might give you an opportunity to upgrade with auto-drain valves and condensation removal and get the leaks fixed.

    it's probably best to centrally locate the sensors. Think like how a "small" non-automatic generator panel is sometimes added for critical loads. You take wires out of the main fuse box, run it to mini transfer breakers and then back in.

    Here's another sensor. You see how stuff gets messy quickly.

    This website tries, but doesn't even come close. Sensors in wireless out. Closed system. What else is new.
    Last edited: Oct 7, 2016