Connector for Movable Object - Page 1
Forum section: electronics / projects

author: rifqidewa
author_rank: Newbie
timestamp: August 16, 2017, 10:04:41 am
content: Hi,I want to design some sort of drawer that have simple connection (2 wire). So lets say i have a connector mounted on movable drawer side and stationary drawer side. When I pull the drawer the connection simply break and when I insert the drawer it will automatically slide into place and make connection. I need physical connection not sensor or anything similar that detect when drawer is in place. I saw this kind of connection in hot swap HDD drive bay. In this case I just want a simple connector for two wires so i don't have to make PCB for mounting each connector. Any of you guys have suggestion what kind of connector I'm looking for? If you have a picture it would be great. I don't have any problem if i need to make some accurate hole in each side since all of the drawer part will be machined.Thanks,-RD

author: ajb
author_rank: Super Contributor
timestamp: August 16, 2017, 11:50:42 am
content: What sort of voltage and current? What sort of positioning tolerances can you guarantee between the two connectors? If your drawer has close enough tolerances to guarantee connector alignment as the two halves are mated, then you can use just about anything.If you can't guarantee that kind of alignment through the drawer's mechanics, you may want a "blind mate interconnect". These have features that help guide the connector housings into alignment before the contacts begin to mate. An example would be Molex's Mini-Fit Jr series, which includes BMI variations, although only with 4+ positions.plug housing--note how the slopes around the connector face help guide the mating connector into position.receptacle housingYou could also design mechanical features around a more conventional connector to accomplish the same thing, although of course you need to make sure the alignment of those features to the connector is good enough.Another option would be to use spring contacts. There are some contact blocks designed for connecting to removable battery packs that may work. If you use one entire block for each of your two connections, then you can have them mate with a single big pad on the other side so that left/right-up/down alignment isn't critical--although such contacts often don't have a very large range of motion, so front/back alignment will still need to be fairly close. There arethesefrom Mill-Max, or gohereand look through the spring-loaded connector options.

author: Rerouter
author_rank: Super Contributor
timestamp: August 16, 2017, 11:53:30 am
content: Use the draw slides as your contacts, and have a micro switch at the back to break it, this way your garenteed to always have good connection (provided low voltage and low current)

author: rifqidewa
author_rank: Newbie
timestamp: August 17, 2017, 03:28:06 am
content: Quote from: ajb on August 16, 2017, 11:50:42 amOh i forgot to mention, my voltage and current requirement is around 24 V and 3 A. I think I can guarantee misalignment within 1 mm but of course if there is some connector that can tolerance greater it would be great for me. I'm looking for something that can easily installed lets say just using bolt and nut or simply snap in place.I think this product might work for me. So for plug i just need to make square hole and for receptacle a square hole and 2 holes. Is this kind of connection good enough for long term use? This drawer will be opened and closed frequently. For wire, is it crimped like in ATX power supply connector right?For now I think I just want to buy connector and install it in my design. It will save me hassle modifying connectorMy friend once suggested me with spring loaded contact but i'm still not quite understand how to install it in my drawer. Is it require PCB to mount this spring loaded contact? I try to avoid making PCB for this.Quote from: Rerouter on August 16, 2017, 11:53:30 amI don't think its a good idea, all of drawer will be made entirely from metals.===============================================================Thanks for your suggestion guys

author: ejeffrey
author_rank: Super Contributor
timestamp: August 17, 2017, 05:02:40 am
content: Can you really guarantee 1 mm? That is pretty good for most drawer mechanisms. Most of the blind mate connectors I have worked with are still designed to work with pretty tight alignment, and to support considerably more contacts. Most drawers mechanisms are designed for pretty sloppy fit. Even if you have a repeatable fit today most drawers are made of sheet metal, wood, or composites which can move over time. A connection that mates perfectly today may not be reliable long term.Do you have a requirement on insertion force? Bigger connectors might have looser alignment tolerances but require more force to open and close the drawer.Since you only have two contacts and have (presumably) plenty of space. I would look at making a sliding spring contact. The idea would be to have a couple of flat plates contacts on the bottom of the drawer and finger springs similar to AA battery contacts on the cabinet. When the drawer closes, the plate slides over the battery contacts. You could make the side-to-side and front-back tolerances as big as you want, and the vertical tolerance could easily be several mm. Installation is easy since the positioning is also low tolerance.I would also revisit whether you need the contacts. If the drawer is not removable, it seems like you could have a flexible cable for power and a microswitch or hall sensor for position sensing. There are flexible segmented "cable snakes" for exactly this purpose in rackmount equipment with sliding rails. You attach the snake on both parts and run wires through it, and it keeps the cables from getting tangled in the drawer mechanism.

author: ajb
author_rank: Super Contributor
timestamp: August 17, 2017, 03:58:28 pm
content: Quote from: rifqidewa on August 17, 2017, 03:28:06 amThe drawings for the connectors will detail the panel cutout requirements. You might find a rating for number of mating cycles somewhere in the product specifications, this would give you an idea of expected lifetime based on the rate at which you need to remove/reinstall the drawer. Note that the Mini-Fit series is not designed to be mated or unmated under load, so your design will need to take this into account. Things like hot-swap power supply modules often have a mechanically interlocked switch, so you turn a lever or something to mechanically unlock the power supply and this actuates a switch that electrically disconnects or shuts down the power supply before it's removed. The process is reversed for installation.QuoteYep, the product pages will specify the compatible contacts as well as other mating connectors.QuoteI think Mill-Max has some spring contacts with mounting ears that you can install directly in a panel and then solder wires to. However I suspect these will be too small to mate reliably unless you have some additional mechanical alignment features. There may be other spring contact options that would be more suitable, I don't know any off the top of my head.Quote from: ejeffrey on August 17, 2017, 05:02:40 amJust as a point of reference, the pair of connectors I linked to above specify a maximum misalignment of 0.05"/1.27mm in any direction. This is determined by the receptacle housing, which is designed to float in its panel so that it will be guided into alignment by the plug housing. The plug housing specifies a maximum misalignment of 0.1"/2.54mm, so perhaps there's another mating connector that will match that and give you a bit more margin.The point about mechanical tolerance and wear is a good one, especially if the drawer will be opened and close "frequently".