Thread: Electrical & CFM

A quick update, I have just found out it is possible to buy a 240 volt contacter that is switchable using a radio frequency (not IR) remote control. A couple of remotes should fix that problem. Now onto the CFM part part of the problem.

Hi Chris

You mention Bill Pentz and it really is worth studying his stuff in detail before you go very far down the dust extractor path. Every time I re-read Pentz I find something new....

Bigger ducts and minimal bends means less friction and turbulence, smooth interiors is much better than ribbed, some plastics require electrostatic protection, all discussed in Pentz.

If you put the wiring inside the ducts could this increase the turbulence?? and would the sawdust, etc "grit blast" the wire insulation??

Cheers

Graeme

Chris,

Assuming you haven't installed a mains switchboard yet, another option for remote switching the cyclone is to have the supply to all the other machines that use the cyclone go through a current transformer. Using a small PLC, you can then detect when one of the machines is in use and switch the cyclone on (via a separate contactor). An added advantage of using a PLC is that you can add a little extra on-time to the cyclone to ensure that all the ducting is cleared when the machine is switched off.

Chris

I already have a sub board and all the machines except one are three phase through this board. The only problem with that is the other three phase stuff hanging off the circuit like the welders, pedestal drill, compressor etc that would start the cyclone when fired up. It looks like the best bet is the remote contactor. if I had to run the wring through the ducting I don't think the abrasion would be that high except at the junctions and it could be shielded there. The beauty of this system is each machine could have a switch on it and as it would only be 32 volt the the fire would be small. .

Now onto the pipe runs, anyone know of any look up tables for frictional losses in given lengths?? The drop from the garage is the best part of 10 metres to where the cyclone will be and there will be at least 10 metres in the workshop. This is getting a bit long me thinks, hence i want to know what the losses are going to be. 150mm pipe ain't cheap and I don't want to buy it until I have the answers. off to Google I guess.

One option ( that I have been using for years) is to use an air switch. ( bought my parts from a pool supplier, but available elsewhere)
They are used to control spa pumps. at each machine you have a small plunger and the small air line is cable tied to the outside of the duct. One push turns the extractor ON another push turns it OFF. From any machine in any sequence.

If you need to add another machine you just add a 'T' connector and another air plunger switch.
I have an electrical background but the air system has a lot going for it. Safe and it works.

Tell me more. Am I right in assuming the air switch sends a pneumatic signal to the electrical switch on the compressor? is the air system self contained so the compressor does not have to be on? You could run this sort of system off a paint ball gas canister instead of using a compressor all the time. We do this in karts to drive the gear change system. Bill Pentz's site really has very little on frictional losses in ducting but I found a good site on how to build blast gates and with a little bit of improvement they will be good. I will have to get the cyclone out of it's boxes and see exactly what I bought three years ago.

The air switch system is self contained. the push buttons are small bellows that push air down a very small tube ( all the buttons/air lines are simply conected using small 'T' connectors like those used in fish tanks etc)
The switch that operates your dust extractor is a latching type switch that uses the air pressure to switch ON ( and stay on) until it receives another pulse of air ( from any of the buttons) whereby it switches OFF.

So simple and you can run quite long runs of plastic hose.

I bought the components from POOLSTORE,( they sell the main switch unit in a box with 240v plugs etc- ready to use for spa pumps etc- called an AIR SWITCH) however you can source the parts individually from electrical sources ( look up farnell or RS components etc)

They can be a bit $$ so shop around. the system might be too pricey for you. I installed mine when remote control units where not readily available.

When assemblying the air hose you might need to punch a very small hole ( with a pin) in the main air line as it can help the system work better. If I get time I 'might' post some photos.

If you use a well known & reputable brand of contactor (Sprechur & Schuh, Telemechanique), different coil voltages are available in both AC & DC. 32v AC is a common coil voltage. Actually, the coils are replacable in these contactors.

Please do not run the 32 volt wiring in the same duct as the 230 volt wiring. It is illegal as per ASNZ3000:2007;
1.5.11.2. Circuits operating at different voltages.
2.7.2. Protection by insulation or separation.
3.9.8. Prevention of mutual detrimental effects between services.

(Below is the most important clause.)
3.9.8.3. Segregation of different voltage levels.
It basically says that cables of high voltage circuits and cables of low or extra-low voltage circuits shall not be enclosed in the same wiring system unless one of the below conditions are met. They are;
1] The low voltage cables shall be double insulated or,
2] All cables or each conductor of a multi-core cable shall be insulated for the highest voltage present or,
3] The low voltage cables shall be installed in a seperate electrical ducting system.

Originally Posted by elkangorito

Please do not run the 32 volt wiring in the same duct as the 230 volt wiring. It is illegal as per ASNZ3000:2007;

elkangorito,

All good points you have made, however, I suspect that the OP used "duct" in the context of air or dust extraction ducts.

Originally Posted by chrisp

elkangorito,

All good points you have made, however, I suspect that the OP used "duct" in the context of air or dust extraction ducts.

Thanks Chris. I'll edit my post accordingly.

First Im not quite certain what this is so excuse me if Im wrong. As I see it you have an extractor on several units and want it switched on when any machine switches on. My method would be low voltage low current and cheap. What you need is a bistable oscillator chip on each machine. When the machine powers up a pulse is taken from the mains line via a capacitor rectified and used to flop the bistable so the voltage on your control line drops to zero, that in turn flips your control unit on the extractor, shuts a power relay and the extractor starts. So every machine has a bistable that bistable when flopped drops a 9V line to earth so all thats needed is a thin speaker type lead connecting all machines Bistable chip is about 40C few capacitors a power supply from dick smith 30 bucks tops the lot. If you wanted to get fancy you could use radio controlled