Use of 9-way D connector for mains. - Page 1
Forum section: electronics / projects

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: September 24, 2014, 04:11:53 pm
content: Hi,I'm just in the middle of repairing a little heated platform for someone. It plugs into this temperature controller.http://www.hcphotonics.com/products2.asp?area=1670&cat=1752&sn=943The heated platform contains a heater and a Pt100 sensor. It connects to the temp controller via a 9-way D connector.While fault finding I discover that the unit is putting out 230v mains on one of the D9 connector pins to feed the heater. The connector is not marked or labelled, anyone's first thought would be to assume it's an RS232 port. Internally, the wires are hand soldered into the solder buckets and not sleeved or heatshrunk.I feel like I ought to condemn this unit on the grounds that it is dangerous by design. There's no sign of a CE mark on it but perhaps it's in the manual which I don't have. Does anyone know what specific clearance/creepage rules are specified for mains so I have some facts to back up my hunch that this thing should go in the bin?Cheers.

author: KJDS
author_rank: Super Contributor
timestamp: September 24, 2014, 04:16:46 pm
content: Creepage and clearance is dependent on many factors, environment, cleanliness etc, however if it walks like a duck and quacks like a duck ...

author: Neilm
author_rank: Super Contributor
timestamp: September 24, 2014, 06:53:02 pm
content: The CE mark should be on a place that can be seen by the user generally the outside. There are some exceptions for instance I believe mobiles are allowed to put them under flaps or the battery. Something like that should have it on the outside.I have had a quick look and none of the D-types I saw gave voltage ratings. Generally I believe the clearance for mains is about 3mm (double). It does sound like this could be a hazard in case of misconnection, it depends what the source of this 230V is. It could be that it is current limited through a suitable resistor and is safe.

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2014, 07:10:57 pm
content: D type can be rated for mains, but only with the appropriate high voltage inserts. Not part of a regular D connector, only available in the Amphenol range as specialist connectors. They are also only rated for 250V if enclosed in a piece of equipment where access to the connector requires you to use tools to open the casing.

author: Dago
author_rank: Frequent Contributor
timestamp: September 25, 2014, 07:12:04 am
content: Quote from: Neilm on September 24, 2014, 06:53:02 pmHeh I've actually seen some cheap D-subs from Digi-key that mentioned a rating of 250 V and 5 Arms. Those are pretty damn sturdy d-sub if they're good for 1 kW....Here is the datasheet:http://portal.fciconnect.com/Comergent//fci/documentation/dsub_economy_range.pdfI wouldn't use them for more than 1 A but...

author: tggzzz
author_rank: Super Contributor
timestamp: September 25, 2014, 08:27:46 am
content: Using components outside their rated values is clearly dodgy.If a serious problem manifests itselffor any reason, what would be the reaction of the civil authorities (police/law) and insurance companies? What would be the consequences for the owner and/or the repairer?

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: September 25, 2014, 11:01:25 am
content: No current limiting.IEC inlet --- 3A fuse----Solid State Relay---- pin 5 of female D9 connector on back panel

author: German_EE
author_rank: Super Contributor
timestamp: September 25, 2014, 11:09:26 am
content: A 9-pin D Connector would not be my choice when using mains voltages. Apart from the possibility of flashover between pins there is also the safety aspect because of the possibility of touching live terminals. Rather than bin the device I would replace the D Connector with something more suitable, maybe a Molex.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: September 25, 2014, 11:10:54 am
content: Haha, just has a closer look and it gets better.Single pole switch on the neutral of the IEC inletMetal case not earthed.It's going in the bin.

author: macboy
author_rank: Super Contributor
timestamp: September 26, 2014, 02:08:19 pm
content: Quote from: DenzilPenberthy on September 25, 2014, 11:10:54 amGood choice. That's theonlysane course of action.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 26, 2014, 02:28:07 pm
content: QuoteJust because a connector is rated for 250v, doesn't mean it's suitable for mains.Mains stuff has to deal with touch-proofing, transients etc.

author: Dago
author_rank: Frequent Contributor
timestamp: September 26, 2014, 03:07:29 pm
content: Quote from: mikeselectricstuff on September 26, 2014, 02:28:07 pmYou are absolutely correct, I was being sarcastic. I'd never even fathom trying to push a kW of mains power through a D-sub connector