Relay coil Set and Reset with momentary switch - Page 1
Forum section: electronics / projects

author: Gowda1
author_rank: Contributor
timestamp: January 14, 2021, 02:12:09 pm
content: Hey Guys,I have a trouble regarding activation of set and rest coil of the Relay which is dual coil-latching. The datasheet has mentioned that to set or reset the coil I need to apply rated voltage for Max 20ms in the coil data specifications section and also mentioned min 100ms Pulse length to set and reset in NOTEs section. I am not sure which one to consider. I would like to know the minimum and maximum time length I can apply to the relay coil to set or reset. I am thinking to do it with momentary SPDT toggle switch ( I am not sure if can go with it ) Do I absolutely need control circuit to set or reset the coil ? or any other method which is not necessarily cheap will do the job? If anyone has any experience with dual coil latching please suggest me on this.PS: Supply for the coil is coming from DC supply

author: fcb
author_rank: Super Contributor
timestamp: January 14, 2021, 03:04:49 pm
content: You could use a capacitor in series with a coil. Probably get away with a sharing a single decent size electrolytic capacitor (with a bleed resistor across it) if you're not pressing the buttons in quick order.

author: macboy
author_rank: Super Contributor
timestamp: January 14, 2021, 03:12:49 pm
content: In the "2. Specifications" table, the line:Quote...refers to the maximum time that the relay will take to set. This is not the same as the amount of time that you must activate the set coil.

author: eblc1388
author_rank: Frequent Contributor
timestamp: January 14, 2021, 06:19:12 pm
content: Quote from: Gowda1 on January 14, 2021, 02:12:09 pmWhen the relay is new, the manufacturer's data indicates the relay will set/reset with a maximum pulse of 20ms. However, the user of the relay(i.e. you)shouldprovide a set/reset pulse longer than that to ensure the relay will definite operate without doubt, both in new condition and in the years to come. The note suggests that the pulse length should be 100ms or more.

author: retrolefty
author_rank: Super Contributor
timestamp: January 14, 2021, 07:27:07 pm
content: Not sure it is possible to activate a dual coil latching relay with a momentary push button switch.

author: capt bullshot
author_rank: Super Contributor
timestamp: January 14, 2021, 07:46:11 pm
content: Quote from: Gowda1 on January 14, 2021, 02:12:09 pm20ms is the minimum pulse duration for a new relay @ room temperature that is required for the relay to set / reset. 100ms is recommended for safe operation under typical operating conditions (old relay, elevated temperature). The maximum pulse length isn't given, it's not critical but maybe limited by coil temperature (the coil is quite low resistance and has 1W / 2W drive power, this will heat the coil). If there was a limit (because the coil would get to hot) I'd expect that to be specified.So driving the relay is fine as long as your drive pulse is longer than 100ms and not continuous (but doesn't matter if it's 200ms or 2s).

author: Gowda1
author_rank: Contributor
timestamp: January 15, 2021, 01:40:42 pm
content: Thank you for the clear answer. But I am also worried about the state of the relay if i used momentary switch. Is there any way I could get to know the state whether its set or reset. May be digital latching or flip flop? Please suggest me on this

author: capt bullshot
author_rank: Super Contributor
timestamp: January 15, 2021, 01:55:15 pm
content: There's one way to know the state of the relay: Read back the contact in whatever way is possible with your application. E.g. connect some lamps or LEDs to the switched circuit to indicate whether it's on or off.

author: Gowda1
author_rank: Contributor
timestamp: January 15, 2021, 02:20:22 pm
content: Yea I thought so. But my application works in 40A and 400Ac rms. I believe LED or lamps are not the possibe solution. Please suggest me any solution with this ower rating

author: capt bullshot
author_rank: Super Contributor
timestamp: January 15, 2021, 04:29:05 pm
content: Neon indicators with proper series resistors will work at 400Vrms