Snap PSU Design Poll - Page 1
Forum section: electronics / projects

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 05:11:59 am
content: As mentioned in another thread.Knob usability kinda sucks, with the binding posts and the compact case.What to do?Dave.

author: PeterG
author_rank: Frequent Contributor
timestamp: March 25, 2012, 06:12:02 am
content: Looking at the knobs in relation to the posts, i think there position would become very annoying very quickly if the power supply was used frequently.I am thinking you could leave the posts where they are and move the knobs closer to the centre and mount them vertically. This would keep the knobs clear of the posts.The resulting larger case would also make it easier for people to mod there power supply.Just my 2 cents.Regards

author: IanB
author_rank: Super Contributor
timestamp: March 25, 2012, 07:43:48 am
content: I don't have a good sense of scale. It's not possible to put the binding posts on the lower left, under the display?

author: Rerouter
author_rank: Super Contributor
timestamp: March 25, 2012, 07:55:22 am
content: was pondering this since you first showed the design, why not binding posts under display, and buttons and encoders on the same side, with the encoders staying where they are, and 4 of the buttons just below (in current picture) them,that doesn't block the display, and means all the controls are nice and packed together while still usable,edit: seems like usual i went and forgot myself, any way of raising the LCD, you where planning a riser board, so the bindings can remain beneath the LCD

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 07:59:29 am
content: Quote from: IanB on March 25, 2012, 07:43:48 amAh, no , sorry. Should have explained the LCD screen takes up almost all of the unused panel space. It's a very tight fit too.Dave.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 08:06:56 am
content: There is a possibility I can mount the rotary encoders on the LCD riser board and have theThe binding posts won't really fit below the LCD, by a fraction.I originally speced in a smaller LCD for this project, and it fitted handsomely, but I really wanted the larger font display and 2x20.Dave.

author: Rerouter
author_rank: Super Contributor
timestamp: March 25, 2012, 08:11:16 am
content: what about 1 encoder and 1 binding post per side?, yes i can imagine this will end in a routing nightmare, but i cant see much more if the binding posts wont fit under the lcd,

author: Psi
author_rank: Super Contributor
timestamp: March 25, 2012, 08:15:14 am
content: Just a random idea.Could use flush mount banana sockets. And even have two sets in parallel (front and back of the case).A typical power supply cable could then be plugged in direct.It's likely that without the wide binding posts there would be more room.You can also get binding posts with banana plugs on the end. So they could be plugged in if binding posts are required.eghttp://rsk.imageg.net/graphics/product_images/pRS1C-2265927w345.jpgHowever the current case is quite small for a power supply, so if a bigger case is needed it's not the end of the world.It would also provide extra room for people to customize the power supply and add extra circuit boards.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 25, 2012, 08:32:48 am
content: I think:Binding posts below the knobs, otherwise the leads will be in the way of the knobs, and anyway the knobs get twiddled more than the binding posts get twiddled so they should be given priority.If it's portable then people wont be putting stuff on top of the box, so there should be a bit 3d space above and in front of the box.Can you just move the knobs up as much as possible, get them further away from the binding posts.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 08:39:15 am
content: I think I may have it sussed.LCD, straight rotary encoders and straight switches all mounted on a front panel PCB soldered at right angles to the underside of main PCB.With vertical binding posts.Should just be enough room...Dave.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 25, 2012, 09:41:38 am
content: Does it really need to be that small - I'd just go for a bigger case. Terminals that close to the knobs will be a PITA.

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2012, 10:46:05 am
content: Rear mounted socket with a breakout box? That leaved the front panel clear, and you can put 2 pin sockets there for a meter to confirm there is a correct output.

author: baljemmett
author_rank: Unknown
timestamp: March 25, 2012, 10:53:05 am
content: Quote from: EEVblog on March 25, 2012, 08:39:15 amThat's pretty much the 'something else entirely' I voted for. Knobs beat switches by a country mile as a control mechanism!I suspect, looking at it, that having the binding posts vertically on the far left of the front panel with the knobs vertically on the right -- shifting the display right as required -- might give the best accessibility, although now I'm wondering about left-handed vs. right-handed usage (wrist obscuring the display during adjustment).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 25, 2012, 11:26:19 am
content: Quote from: baljemmett on March 25, 2012, 10:53:05 amif it's a graphic LCD, you could solve that by having the option to turn the whole thing upside down in the case to allow controls to be at the left or right.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 25, 2012, 11:27:37 am
content: If space is tight, you definitely want knobs to be above each other to allow better finger access, ditto binding posts.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 25, 2012, 11:57:48 am
content: - smaller LCD, binding posts mounted bottom-centre- 2mm banana sockets instead of the biding posts- even more exotic connector than 2mm banana sockets- no connectors, just two wires with 4mm plugs at the end- three-way jog switches (incl. centre switch) instead of the encoders

author: BravoV
author_rank: Super Contributor
timestamp: March 25, 2012, 12:28:09 pm
content: What ever the final decision, just a thought if the knobs and the sockets are too close, put a software or hardware knob lock mechanism.Remembered a friend toasted his circuit when he was accidentally knocked & turned the voltage knob when fixing the power connection at the binding post which is the coarse voltage adjustment knob that was placed nearby, it is a diy bench psu that has really poor front panel layout.

author: WBB
author_rank: Regular Contributor
timestamp: March 25, 2012, 01:25:20 pm
content: Mount the display centered, as high as practical. Knobs mounted vertically left of display, binding posts vertically right of display. Row of buttons below the display.If there's room it might make a nice layout.

author: WBB
author_rank: Regular Contributor
timestamp: March 25, 2012, 02:26:20 pm
content: Another possibility would be to mount some type of flush mount buttons, that could be operated by feel, into the top of the case.

author: T4P
author_rank: Super Contributor
timestamp: March 25, 2012, 04:40:53 pm
content: How about a push-pull pot to disable the output when pressed in ?Saves months of agony over accidental voltage knock over .

author: firewalker
author_rank: Super Contributor
timestamp: March 25, 2012, 05:21:41 pm
content: Is a push button embedded to the rotary encoders? Use one rotary encoder and take advantage of the push button to toggle between voltage and current?Alexander.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: March 25, 2012, 07:32:44 pm
content: Why not move the terminals to the back? No problem to access the rear for a portable device like this.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 25, 2012, 08:27:35 pm
content: QuoteAs the front panel will be PCB. the buttons could be cap-touch pads, so could be sized to fit the space, and if necessary overlap the border of the LCD glass behind the panel which you couldn't do with conventional buttons. You'd probably want a piezo sounder to give feedback clicks.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 25, 2012, 09:06:08 pm
content: The binding posts look fairly close. Is there space to make them the standard 3/4" spacing for use with double banana plugs? I would bite the bullet and go for a bigger case. Then you can keep the knobs you want, nice binding posts, and keep enough finger clearance.

author: markus_b
author_rank: Regular Contributor
timestamp: March 25, 2012, 09:22:56 pm
content: Quote from: EEVblog on March 25, 2012, 08:39:15 amPlaying around with cardboard and drawing the result I've found a solution I like. I don't know the precise size of your display, I've use the size of one of my choice.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 09:27:54 pm
content: Quote from: Dave.S on March 25, 2012, 04:40:53 pmPlenty of ways to implement a software lock, no need for push-pull switch.Dave.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 09:31:09 pm
content: Quote from: baljemmett on March 25, 2012, 10:53:05 amYep, that's the solution I'm looking at, exactly like Markus's drawing.Dave.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 25, 2012, 09:40:22 pm
content: Quote from: EEVblog on March 25, 2012, 09:31:09 pmAs I said, make it reversable. If it's all symmetrical, you may be able to do it without having to turn the LCD upside down. If all that's on the PCB is terminals, encoders and display, it may be feasible to dual-footprint it so the PCB can be populated on either side. Ditto the front panel PCB - legends on both sides.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 09:47:18 pm
content: Quote from: mikeselectricstuff on March 25, 2012, 09:40:22 pmYeah, might be feasible, but it seems like a lot of trouble to go to for what really is hardly a problem at all (left/right handed people).Dave.

author: ivan747
author_rank: Super Contributor
timestamp: March 25, 2012, 09:50:14 pm
content: Use different colors or shapes for the knobs, that way you can use them to control software functions like it is done with some oscilloscope knobs.

author: ivan747
author_rank: Super Contributor
timestamp: March 25, 2012, 09:53:26 pm
content: Quote from: ivan747 on March 25, 2012, 09:50:14 pmWhat I mean is that it is easier to identify a particular knob if it has a different color or shape. Also, I don't see much room for big labels.

author: ivan747
author_rank: Super Contributor
timestamp: March 25, 2012, 09:58:17 pm
content: Quote from: BravoV on March 25, 2012, 12:28:09 pmWhat about an encoder that can be pushed in, similar to how you use click a Playstation or Xbox joystick, and LEDs indicating it is locked? Dave is going to hate us for making him add another IO expander.)

author: ivan747
author_rank: Super Contributor
timestamp: March 25, 2012, 10:04:10 pm
content: Quote from: EEVblog on March 25, 2012, 09:47:18 pmJust include the symmetrical footprint and solder everything, even the binding posts. If a left handed user gets pissed out with the layout, he/she will desolder the parts and relocate them.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2012, 10:15:59 pm
content: Quote from: ivan747 on March 25, 2012, 10:04:10 pmYou would also need to flip the panel as Mike mention.It just gets rather messy, and I really don't see any major benefit, or problem in the first place for left handers.Dave.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 25, 2012, 10:17:14 pm
content: I'm a left hander,the left-right thing is not an issue, so thanks for the thought but please don't complicate things unnecessarily.

author: Rerouter
author_rank: Super Contributor
timestamp: March 26, 2012, 02:33:29 am
content: it only matters for left hander's when where holding a pen, lab gear makes no difference what hand is used,

author: Alex_arg
author_rank: Contributor
timestamp: March 26, 2012, 05:10:30 pm
content: Hi Dave !, i think you should pick a new box taller than this. Also , i would put the pushbuttons below the display.Are there concentric rotary switchs ? (Like old oscilloscopes), you could save some space with one of these.There are small jacks for output, but i really like those you're using, with a nut to wrap the wire directly.BTW, the PSU it's getting pretty, thanks for all your work.

author: kodai
author_rank: Contributor
timestamp: March 26, 2012, 07:48:43 pm
content: I'm for keeping with the small form factor if you are sticking with two 18650's. If you go with a larger case, then reconsider the extra cost and go with 3 or 4 18650's. I cant wait for this little fella to be born so I can stop dragging out an extension cord for my PSU's when my little, cramped workbench is full. I already use 18650's (and 17670's, 14400's and cr123's for all my vaping gear), so I'm ready to go on batts and chargers.