uSupply Keypad Design

[EEVblog]

As the poll says, what would you prefer for the input method on the new uSupply.
Yes, there is deliberately NOT an option for knobs, it's keys only, I won't explain why, it just is.

Separate up/down Voltage and Current control arrows with velocity control for holding them down, or a numeric keypad were you press say 3.3 and then the V or I key.

What say you.

[CopperCone]

Should be both like wavetek equipment. Especially if you can jump to different preset voltages for ease like 3.3 5 12 15

[BrianHG]

I require the step up/down when first time powering up a new prototype.  When I like to inch up the current so the supply will up the output voltage until the consumption current is cleared and the supply switches from CC to CV mode.

But, a lot of times I need to set a voltage and current value immediately.

So, I cannot answer your poll, since I need both numeric entry to set my position, and a single step up/down arrows which by default move the voltage up and down by default when in CV mode, but if the supply switches to CC mode, the same arrows should switch over to adjusting current limit until the output switches back to CV mode.  In other words, the same as my current BK Precision bench supplies.



And an optional module for an add on opto-isolated RS232 port would be handy too.
I also agree with you that a spinning rotary knob is dangerous unless it's indented single step with indents stiff enough and large enough that you can never make a mistake by accident.  Otherwise, it's a potential magic smoke moment for what you are working on...  Also, wear out and damage on these rotary encoders may achieve the same problem.

[jbb]

Oh, this is a hard one.

Can I be a pain and say “both”? (In the absence of knobs.) I’d like a voltage up/down, a current up/down and then a numeric for quick entry.

Looking forward to seeing the results.

[cat87]

Right now I'm thinking of a scenario where I need to set a certain voltage/current value with the keypad, then slowly change that in mV or hundreds of mV steps with the up/down keys.
So, just to make things harder for you, I'd go with "both"   

[TheUnnamedNewbie]

I would have to go with the "both" option. But if that is really not possible, I have to say I prefer numerical keys, though it depends on the resolution. Much easier to go from 2 V to 15 V by just pressing "Vset - 1 - 5 - enter" or something. Up-down I would mainly use to just shift tiny amounts to see what the influence of small shifts in supply is on performance.

[jbb]

Sorry Dave, we're blowing up your poll...

[BravoV]

Oh, this is a hard one.

Can I be a pain and say “both”? (In the absence of knobs.) I’d like a voltage up/down, a current up/down and then a numeric for quick entry.

Looking forward to seeing the results.

Hopefully the firmware will be hack-able, then turn the numeric keys into 4 directions arrow keys by some unique sequence like press & hold certain button to activate it for example.

[mikerj]

No encoder   I really do not like bench supplies without adjustment knobs for manual use (fine for automated test etc.).

With only push button input,  both direct entry and an increment/decrement would be preferable.  With only direct entry, multiple small adjustments become slow and very error prone, and requires you to concentrate on the PSU keyboard rather than your circuit or the instruments attached to it.  With only increment/decrement setting a specific value becomes a bit of a chore, but at least you can adjust the voltage up and down whilst looking at another instrument.

If it really has to be only one or the other then the only sensible option would be an increment/decrement system, and you should be able to choose which significant digit to operate on, and it should be difficult to accidentally change the active digit (e.g. maybe require a longer press).

[CopperCone]

  :popcorn:yes rotary encoders can be a pain in the balls especially when they malfunction and jump voltages in carefully sequenced things. I would trust a potentiometer more unless there is rate limiting code in the mcu control algorithm. I.e. halt the jump of the computed value is greater then some integer

[ArdWar]

How many digits will be available? Can we have both keypad and up-down? It can't be that hard to add 2 more buttons (the software complexity might be, though), but if I have to choose, I'm leaning to keypad input. Having up-down button might be nicer if I want to ramp things up/down, but sometimes allowing supplies change values while operating might not the best for certain scenario.

:popcorn:yes rotary encoders can be a pain in the balls especially when they malfunction and jump voltages in carefully sequenced things. I would trust a potentiometer more unless there is rate limiting code in the mcu control algorithm. I.e. halt the jump of the computed value is greater then some integer

Wouldn't these design use a incremental encoder? If values jumped around then 99% of the times that's a software problem, and if it jumped around because of a dodgy intermittent signal then it maybe still a software problem.

[SiliconWizard]

Both entry modes are useful in different situations IMO. So ideally, that would be great to support both.

As an alternative to a plain numeric entry that would be a compromise, you could allow up/down operation either on the whole value or on a specific decade (that one could select with the push of a single button or with arrows). In this mode, the selected decade digit could be blinking. This would allow quick entry while keeping the number of keys at a minimum.

Just my 2 cents.

[GeorgeOfTheJungle]

Lab equipment without knobs?? Are you kidding me? Up/down buttons are a poor substitute for proper fine and coarse knobs imo. The keyboard is a must only for the plus/pro model.

IOW, WRT knobs, the more the better :-)

[Lightages]

I voted for keypad, but both would be much better. Maybe a function like hold the I or V button while pushing 2 for down increment and 8 for up.

[GeorgeOfTheJungle]

I also agree with you that a spinning rotary knob is dangerous unless it's indented single step with indents stiff enough and large enough that you can never make a mistake by accident.  Otherwise, it's a potential magic smoke moment for what you are working on.

In all my life I never ever had this problem, not even once. (I'm 54).

[madires]

I'd go for the numeric keypad and add an alternative up/down mode, like the numpad of a PC keyboard.

[GeorgeOfTheJungle]

Then if you want to step up once and it wasn't in incremental mode you type in an 8 and the magic smoke escapes...

[madires]

That's easily fixed by a "Set" button:
- enter the value or push up/down keys
- uSupply shows the new current/voltage but keeps the old value still set
- confirm with Set key -> new value gets applied
- if not confirmed within x seconds -> update display with old value

[The Soulman]

Both entry modes are useful in different situations IMO. So ideally, that would be great to support both.

As an alternative to a plain numeric entry that would be a compromise, you could allow up/down operation either on the whole value or on a specific decade (that one could select with the push of a single button or with arrows). In this mode, the selected decade digit could be blinking. This would allow quick entry while keeping the number of keys at a minimum.

Just my 2 cents.

What he said.

[BrianHG]

Dave, do you have a photo of the keypad/up-down buttons you intend to use?
Or will you be making a custom membrane keypad?

[GeorgeOfTheJungle]

That's easily fixed by a "Set" button:
- enter the value or push up/down keys
- uSupply shows the new current/voltage but keeps the old value still set
- confirm with Set key -> new value gets applied
- if not confirmed within x seconds -> update display with old value

...and then the UI is a disaster :-) fine+coarse knobs are better imo.

[max_torque]

I don't care (about having direct voltage input or Up/Down keys).

Because, if it hasn't got knobs, i'm not buying it anyway............   

[Maxlor]

If it has to be just one or the other, give me up/down keys. While those make just setting a voltage more cumbersome, the advantage of being able to gradually change the voltage whilst not looking at the keypad (but instead at, say, a scope screen) is worth it.

[mikeselectricstuff]

Up/Down keys should probably not have any acceleration on a power supply - should just be a simple auto-repeat style at a constant speed, with some way to seperately control that speed ( like a digit select).

Given the choice of numeric or up/down, then it would have to be the latter as there will always be times you want to increase/decrease the output, and numeric only would be useless for that, but there are also times you want to enter a specific voltage numerically.

A possible third way, given the "buttons only" constraint, would be an up/down button pair (with auto-repeat) per digit.
This would allow any voltage to be quickly reached, as well as up/down adjustments.
This would need fewer buttons than numeric entry, but still provide a quick way to get to a specific voltage

[plazma]

Up/down + left/right for selecting the digit.