Relay Design and Wiring

[paulgill28]

Maybe not the channel Spoon was thinking of but one called Technology Connections has done some features on old pinball machines.

Ladder logic can absolutely represent physical relays, that's where it started. In regards to your system, I wouldn't switch the extractor through the 8-pin relay, their contacts are not up to the job despite saying 10 Amp. Rather I would use the relay to switch a stronger contactor that powers the extractor.

Keep working on your diagram, as Dave said there are some issues that will stop it working as you intend so come up with a V2 and we'll take another look.

I have updated the circuit diagram (see Rev.1 attached) having introduced another 8 pin relay and another momentary push button switch to overcome my lamp illumination problem from previously. I think the logic of the circuit now works.

I hear what you say about contactors which is what I originally looked at but concluded as the max current draw of the extractor is only just over 5 amps I could use relays, especially as I can get a good deal on them. Contactors are much more expensive so opted for the relays. Given that the system will only get occasional use and extraction will never be for more than a minute or two each time I figured relays would be cheaper overall even if one fails and I have to replace it. However now that the return current for socket outlets 1, 2 & 3 have to go through relay CR3 I might be inclined to see if I can find a contactor with one NO and one NC switch as the current draw for the power tools could be as high as 10.5 Amps for my router table. Only one power tool will ever be in operation at once. Haven't so far found a suitable contactor at reasonable cost that can be DIN rail mounted.

I've also attached operating instructions for the circuit with all the switch states for each button operation. Still working on a revised ladder diagram for these circuit revisions.

Any comments would be gratefully appreciated.

 

[James]

LC1D09P7 | Schneider Electric LC1D Series Contactor, 230 V ac Coil, 3-Pole, 9 A, 4 kW, 3NO, 690 V ac | RS

uk.rs-online.com

 

[paulgill28]

LC1D09P7 | Schneider Electric LC1D Series Contactor, 230 V ac Coil, 3-Pole, 9 A, 4 kW, 3NO, 690 V ac | RS

uk.rs-online.com

Thanks. Already come across this one, but at £50 seems expensive for what I need.

 

[ElectroChem]

Thanks. Already come across this one, but at £50 seems expensive for what I need.

Fusebox INC202 Contactor DP 20A 230V N/O 2 Pole Heating Lighting Din Rail Mount

Fusebox INC202 Contactor DP 20A 230V N/O 2 Pole Heating Lighting Din Rail Mount- £6.59

lamplec.co.uk

 

[paulgill28]

Fusebox INC202 Contactor DP 20A 230V N/O 2 Pole Heating Lighting Din Rail Mount

Fusebox INC202 Contactor DP 20A 230V N/O 2 Pole Heating Lighting Din Rail Mount- £6.59

lamplec.co.uk

This contactor you suggested unfortunately only has two NO switches rather than 1 NC and 1 NO required for the CR3 current sensing bypass relay/contactor, but I have now found an inexpensive one which has 1 NC and 1 NO and is rated to 25 amps:

Heschen Household AC Contactor, HS1-25, 2 Pole 1NO 1NC, AC 220V/230V Coil Voltage 25 Amp, 35 mm DIN Rail Mount which is rated as Ui~ 500V, Ue~ 250V, Ie (AC-7a) 25A and Ie (AC - 7b) 9A.​

Do you know whether this would be OK for a 2,400W 230VAC Router motor which I presume can have a max load of 2400/230=10.43 Amps? Ie (AC - 7b) for this contactor above seems to be stated as 9 amps.

I understand Utilization category AC-7b under the IEC/EN 61095 standard describes conditions for controlling domestic motor loads, including those with high starting currents, like washing machines, dishwashers, and other household appliances with motors.

While the specific maximum load under AC-7b can vary depending on the manufacturer, design, and specific application, this category generally accounts for significant inductive loads, with higher inrush or starting currents. The key focus in AC-7b is the ability to withstand these high starting currents and control high-power motors without damage or failure.

That said, there isn't a universally specified maximum load in terms of wattage or amperage. Instead, the limits are defined by specific products that comply with this category. Factors that determine a device's suitability for AC-7b include:

• Motor power: How much power the controlled motors draw during normal operation.
• Starting current: The initial surge of current when the motor starts. This can be several times higher than the running current.
• Switching frequency: The expected frequency of turning the motor on and off.

Unfortunately I don't have the specification load profile for the router motor other than its Voltage and Power rating, 10,000 - 22,000 RPM, relevant standards EN 60034-1:2010 and the Low Voltage Directive 2006/95/EC and it has a soft start feature which I presume avoids higher start up loads.