Current sensing switch with run on feature - Page 1
Forum section: electronics / general

author: jamesbeard
author_rank: Newbie
timestamp: June 15, 2023, 02:35:39 am
content: Hi all.Looking for a switch or module to allow automatic starting of one device when another runs, with a run on feature.Concrete example is a carpentry workshop where we want the extraction fan to start running when the saw starts, and then keep running for a minute after the saw stops.Even some search terms to look for would be a help. Have tried "current sensing switch", "run on" and a few other terms, though not quite finding what we're after. Detection of current flowing would ideally be single / 3 phase independent (variety of tools) but all fans to be driven are 240v single phase.Many thanks1James

author: Whales
author_rank: Super Contributor
timestamp: June 15, 2023, 03:59:40 am
content: You can get power boards thatalmostmatch what you want, but I'm not sure how long they stay on after the main device stops pulling current. These are mainly targeted at the TV market (for turning on and off nearby appliances like audio amplifiers).https://www.jaycar.com.au/smart-powerboard-with-energy-meter/p/MS6152

author: Whales
author_rank: Super Contributor
timestamp: June 15, 2023, 04:13:47 am
content: It's a shame that these cheap "DIN rail protection relays" have limited IO and break the same wire that they measure:https://www.ebay.com.au/itm/204309414055They even have an adjustable timer post-trip. All for <$20AUD shipped.EDIT: Perhaps a combo of these two parts? I'm not sure of the quality or safety of these no-name mains electronics, could be quite shady? I'd take them apart to evaluate their safety first before using them, but I don't know your skill level.Current sensor with on/off output (not analog output, "current detection switch"):https://www.aliexpress.com/item/1005003787232919.htmlConfigurable timer ("delay-off" mode wanted) with 16A output:https://www.aliexpress.com/item/32881831418.html

author: MarkL
author_rank: Unknown
timestamp: June 15, 2023, 01:02:57 pm
content: Take a look here:https://isocketproducts.com/It has the basic function you want, but 1) the run-on time is shorter than you want and 2) it appears to be 120VAC only.If you want to control a 240VAC fan, you could have this device control a time delay relay that has a 120VAC input and it, in turn, can switch the 240VAC for the fan and leave it on for a settable delay.I have an older model of this and it works well with a table saw and shop vacuum.Here's one with a 240VAC option where the tool sensor and vac switch are wireless:https://www.rockler.com/ivac-pro-tool-switch-wireless-dust-collection-controller-system-ivac-pro-switchI'm sure there are others out there.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 15, 2023, 01:26:57 pm
content: You mean a master/slave switch?https://www.conrad.nl/nl/p/kemo-m103n-master-slave-schakelaar-module-230-v-ac-1091973.htmlhttps://www.kemo-electronic.de/en/Transformer-Dimmer/Switches/Modules/M103N-Master-Slave-switch-230-V-AC-400-V-AC-.phpAlternatively you can make your own with acurrent monitoring relayand atimer relay.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 12, 2023, 05:50:41 pm
content: It seems that the socketproduct is a good choice. However, if I need one I can make one with parts I have laying around the house but if I were to buy them it would not be cheap. I would use a current transformer with analog output. A PLC with analog input. An SSR to turn on the vacuum.