4 channel relay board - Page 1
Forum section: electronics / projects

author: blackjames
author_rank: Regular Contributor
timestamp: May 10, 2012, 10:20:12 am
content: hi,i've just designed a 4 channel relay pcb rated for 250Vac. the board measures 89mm by 78mm. each relay has a led to show its current state. control voltages should be about 5v to 12v. the relays have 5v coils. the pcb also has an optional 5V regulator if you want to run it off 12V or maybe 15V. with parts from rs components, including GST and pcb is about $22 australian. do you think this is a kit worth selling for about $35. this is my first product design to sell. the price above is for a batch of 25, also do think i could sell so many?thanks for any help.

author: blackjames
author_rank: Regular Contributor
timestamp: May 10, 2012, 10:20:53 am
content: i forgot to add: the relays are rated at 10amps.

author: Galenbo
author_rank: Super Contributor
timestamp: May 10, 2012, 11:09:05 am
content: I don't think it's becoming a bestseller.A quad Relaydriver is very engineered-out, everyday product.Many brands have it.Here's a quality product for 16euro:http://www.conrad.nl/ce/nl/product/190980/

author: Psi
author_rank: Super Contributor
timestamp: May 10, 2012, 11:29:14 am
content: If you put a cheap micro on there and some dip switches you could implement all sorts of timing functions.On delay, Off delay, Toggle delay etc.And all it would cost is maybe $3-4 extra, for a micro, DIPswitches and maybe a trimpot.It would set it apart from generic relay boards without costing much more.

author: nctnico
author_rank: Super Contributor
timestamp: May 10, 2012, 03:09:25 pm
content: Don't bother:Search for oder number 197720 onwww.conrad.com. I've used these cards a lot for automated testing. They are very easy to use and very reliable. There is also a 230V version (order number 197730).

author: GBarron
author_rank: Newbie
timestamp: June 01, 2012, 03:17:05 pm
content: Please forgive my lack of knowledge, but I am looking for a relay board to use with mains electricity and an MCU to control power to devices such as a TV or DVD player. Is this the kind of product I should be using for that?

author: Galenbo
author_rank: Super Contributor
timestamp: June 02, 2012, 02:23:25 pm
content: You could be using this kind of product.Depending on the exact specs of your MCU.

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2012, 11:52:07 pm
content: Just to clarify things: Velleman products are never safe to use with mains! Even if the manual says so. Their designs always lack the necessary isolation distances. The relay board Conrad sells under order number 197730 has the necessary isolation distance to handle mains voltages safely.

author: casinada
author_rank: Frequent Contributor
timestamp: June 03, 2012, 04:51:06 am
content: http://www.ebay.com/itm/160778904666?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649$6 + Free Shipping

author: Zero999
author_rank: Super Contributor
timestamp: June 03, 2012, 10:21:23 am
content: Quote from: casinada on June 03, 2012, 04:51:06 amI wouldn't trust such a cheap product for mains.

author: Galenbo
author_rank: Super Contributor
timestamp: June 07, 2012, 07:53:21 am
content: Quote from: nctnico on June 02, 2012, 11:52:07 pmThe distance between the NO NC COM and other connections on the velleman board is minimum 2mm.What's the required distance? Where can I find normation on that?

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 07, 2012, 08:20:21 am
content: Quoteouch!Quotea good friend sent me this standardhttp://www.smps.us/pcbtracespacing.htmlQuote from: hlavacbut i saw another standard contradicting in there saying iirc 1-2mm is acceptable. and that for 500V, for mains, should be lower.

author: nctnico
author_rank: Super Contributor
timestamp: June 07, 2012, 10:55:58 am
content: Quote from: Galenbo on June 07, 2012, 07:53:21 amFor 230V mains you'll need 3mm (for grounded devices) or 6mm (for double isolated devices) clearance between the mains and low voltage circuits. The problem with Velleman is not the distance between the contacts but none of their boards have sufficient clearance between low voltage and mains circuits.Elektor has an article on the subject:http://www.elektor.com/magazine/construction-electrical-safety.83362.lynkxRun this through Google translate to get an article with picture:http://www.elektor.nl/service/zelfbouw-veiligheid.685243.lynkxNote that this article is written for Dutch / European standards.Edit:QuoteThese clearances are for traces without voltage spikes. Mains can contain large voltage spikes so you will need more clearance than you might expect based on formula's to calculate arcing distance.

author: mukymuk
author_rank: Contributor
timestamp: June 07, 2012, 05:29:03 pm
content: http://www.ebay.com/itm/Four-4-Channel-5V-Relay-Module-Expansion-Board-For-Arduino-PIC-AVR-ARM-MCU-DSP-/150824244290?pt=LH_DefaultDomain_0&hash=item231dd35442#ht_5480wt_954For small kit-type projects look on ebay and see what China is selling. Don't try to sell stuff that they are selling cause you'll lose. They are very good at making cheap small electronic kits.Like Psi said, make it unique and you might have something. At least for awhile.