Battery Power Supply

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tortugaranger

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Battery Power Supply
« on: 6 Aug 2015, 05:44 pm »
We've been circling around the subject of power supply for quite some time here in Tortuga land. While there are numerous considerations and applications, the bottom line is we will be introducing a battery power supply product fairly soon. In fact, I'd like to have it ready for RMAF15 in Denver which is the 1st week of October - at least in final prototype if not production. Here's an update on what's coming with respect to the battery power supply.

First of all there's our existing lineup of LDR preamps which currently uses either an external linear regulated "wall wart" or an internal hybrid switch mode PS to provide 12 V. Our LDR controller board also uses 5 V that is also supplied via a DC-DC switch mode regulator with very nice specs. More recent investigations suggest we can achieve the best possible performance using clean DC power from a battery based supply. However, to get the maximum benefit from this approach we will be changing over to a 5V linear regulator with noise specs down in the handful of microvolts vs. the current few millivolts. Retrofitting existing controller boards/preamps with this new linear regulator is doable but challenging as it involves complete removal of the board from its chassis and careful desoldering/removal of the existing 3 pin regulator. If not done very carefully this can end badly with pulled traces and a bricked board. There are likely to be benefits to running off a battery supply even with the existing 5 V regulator left in place on existing units.

Next, we've been slowly working towards a solid state buffer design that will require a split voltage supply. It's essential that any buffer not degrade the sound quality of the LDR attenuator and that means a pristine source of power. Doesn't get more pristine than battery. As with the controller board itself, a buffer doesn't draw that much current so a decent size sealed lead acid battery with a few Amp-Hours of capacity will last a very long time (at least 24 hours of continuous use) running on battery power before needing to kick in the charger.

Closely linked with the solid state buffer is our future integrated headphone amp that will actually be variant of our buffer but with the necessary gain required to drive cans. This will also require a split level power supply which will be provided by batteries to ensure the best possible sound quality. Of course when using batteries (+12 V) and needing split level (+/- 12 volts), this means a pair of 12 V batteries (or single 24 V batterr) plus a rail splitter design to achieve a virtual ground. We believe we've identified a really nice approach to this where the same basic design can supply either just single +12 V or split +/-12V depending on how the board is populated with parts.

Going one step further we also have plans for a fully integrated LDR based amp. This amp will need a conventional "live" power supply that is beyond the practical limits of batteries. However, depending on how things go with the battery for the LDR controller and buffer, we may still include a battery as part of the integrated amp for everything but the amp driver stage itself.

Now, back to work!  :thumb:
Best,
Morten

uraqt

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Re: Battery Power Supply
« Reply #1 on: 16 Aug 2015, 05:19 pm »
I am super excited about the battery power. I would suggest that you use USB power to charge that battery.  : ) Everyone has usb wall warts  : )

Also we could use usb battery packs to charge the built in battery  : )

http://thewirecutter.com/reviews/best-usb-battery-pack-travel/


Thanks

C

tortugaranger

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Re: Battery Power Supply
« Reply #2 on: 17 Aug 2015, 01:12 pm »
I am super excited about the battery power. I would suggest that you use USB power to charge that battery.  : ) Everyone has usb wall warts  : )
Also we could use usb battery packs to charge the built in battery  : )
http://thewirecutter.com/reviews/best-usb-battery-pack-travel/
Thanks
C

As it turns out we've been trying out various approaches to battery charger design and have decide to use a 5 VDC USB source to power the charger. Internally we have to convert the 5 VDC to 12 or 24 VDC which is quite doable using a simple switching DC-DC converter. During normal operation off of the battery, the charger system gets disconnected from the charger circuit so there's no concern about noise bleed-through to the battery power.  :thumb:

robertopisa

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Re: Battery Power Supply
« Reply #3 on: 25 Aug 2015, 03:29 pm »
Interested too... are you using Belleson regulators?

-R

tortugaranger

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Re: Battery Power Supply
« Reply #4 on: 25 Aug 2015, 05:47 pm »
As it turns out we've been trying out various approaches to battery charger design and have decide to use a 5 VDC USB source to power the charger. Internally we have to convert the 5 VDC to 12 or 24 VDC which is quite doable using a simple switching DC-DC converter. During normal operation off of the battery, the charger system gets disconnected from the charger circuit so there's no concern about noise bleed-through to the battery power.  :thumb:

Looks I'm going to have to back away from the above statement. After further development testing we've concluded that driving our battery/charger with a 5 VDC USB source simply isn't robust enough. Not that it couldn't be made to work but the current limitations of USB during charging was a constraint I didn't want to live with. More importantly we intend for this board design to be able to also supply a split rail +/- 10-12 VDC around a floating ground which will be driven by a pair of 12 volt batteries in series. This means charging into 24 volt system. Pumping 5 V up to 24+ needed for charging, while technically doable, was really pushing things especially given the current levels during charging. A split voltage isn't a requirement for the LDR preamp controller board which only needs +9 to 12 V but it is a requirement of our future SS buffer and headphone amp which will use this same board. So bottom line is the battery PS/charger will be run off an AC source and conventional rectified linear regulated DC. During normal operation the battery will be disconnected from the charging circuit.

tortugaranger

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Re: Battery Power Supply
« Reply #5 on: 25 Aug 2015, 06:19 pm »
Interested too... are you using Belleson regulators?
-R

As things stand now the battery PS output for the LDR preamp controller will not be regulated but will instead be at the nominal voltage level of the battery which will likely never exceed 13.5 volts and will drift down towards 12 volts as the battery discharges. At 11.8-12.0 volts, a nominal 12 V sealed lead acid battery will be discharged down to 40% below which it's not recommended. At that level the charger will automatically kick in.

The LDR preamp controller doesn't require, nor would it benefit from, a regulated supply per se. The controller board doesn't require a high bandwidth dynamic power supply as do conventional preamps. It does however like clean, low noise power. The  documentation on the LDR3x controller does strongly recommend a regulated 12 VDC supply but the reason for the regulation is to avoid exceeding the upper voltage limit of one of the board's op amps which goes snap, crackle pop somewhere around 16 V or so. Unregulated 12 V supplies can easily drift up into that range depending on the AC main voltage, transformer ratio etc.  This concern can be avoided by opting for our high precision op amp upgrade which also benefits auto calibration accuracy.

To complicate the explanation the battery system does have on board regulators but their sole purpose is generating a split voltage supply with a floating ground. There will be 2 variations on this battery PS, let's call them PS12B1 and PS12B2.  B1 will simply provide a nominal unregulated yet filtered 12 VDC direct from battery which will be for powering the LDR preamp controller board.  B2 will provide split +12/-12 with floating ground for powering critical op amps etc on our future SS buffer and headphone amp.

The buffer and headphone amp will both have dedicated +/- low dropout linear regulators to firm up that split supply coming from the B2 battery but these regulators will be on the buffer/amp boards. We are planning on using regulators built around TI's TPS7A4700 low noise (~4 uV RMS) regulator chip. While no rival to Belleson's ultimate proprietary regulator, we'll be able to offer Belleson's as a potential upgrade.

While we could have put final +/- voltage output regulators in the B2 itself, it's best to have such regulators as close as possible to destination devices being powered.

robertopisa

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Re: Battery Power Supply
« Reply #6 on: 26 Aug 2015, 12:55 pm »
Sounds cool Morten, please add me to the queue for PS12B1...
-Roberto

rif

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Re: Battery Power Supply
« Reply #7 on: 26 Aug 2015, 02:48 pm »
You mention SLAS - have you considered Nicd? Just curious

tortugaranger

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Re: Battery Power Supply
« Reply #8 on: 26 Aug 2015, 03:16 pm »
You mention SLAS - have you considered Nicd? Just curious

While there are advantages to both, sealed lead acid (SLA) batteries are substantially lower cost, proven and reliable. NiCd would easily double/triple the cost (or more) of the final product. I found that difficult to justify. Once big advantage of NiCd is energy density but since we're going to use our existing enclosure designs we have room for high enough capacity SLA battery. NiCd is always an option in the future.

neilgrobson

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Re: Battery Power Supply
« Reply #9 on: 3 Sep 2015, 09:38 pm »
I  am using a specialised audio battery supply for my Tortuga LDR1 ,it is powered by a 12 volt 7 amp sealed lead acid battery (Yuasa).Designed with intelligent charge discharge cycles,and auto cut off when 10.5 v is reached(after a previous low battery warning).I hope to buy a newer model Tortuga soon.Do you know when Tortuga will switch to the newer spec internal power supply more suited to battery use?

http://www.kingrex.com/download/KingRex%20SLAP%20power%20supply%20unit%20-%20user%20manual.pdf

http://www.yuasabatteries.com/pdfs/NP_7_12_DataSheet.pdf


tortugaranger

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Re: Battery Power Supply
« Reply #10 on: 3 Sep 2015, 09:49 pm »
I  am using a specialised audio battery supply for my Tortuga LDR1 ,it is powered by a 12 volt 7 amp sealed lead acid battery (Yuasa).Designed with intelligent charge discharge cycles,and auto cut off when 10.5 v is reached(after a previous low battery warning).I hope to buy a newer model Tortuga soon.Do you know when Tortuga will switch to the newer spec internal power supply more suited to battery use?

http://www.kingrex.com/download/KingRex%20SLAP%20power%20supply%20unit%20-%20user%20manual.pdf

http://www.yuasabatteries.com/pdfs/NP_7_12_DataSheet.pdf

We are close to finishing development work on the battery supply and expect to have the new "battery friendly" voltage regulator available for new builds in about 2 weeks. We plan on having the battery supply etc. up and running at RMAF in Denver next week. Production of all that will start later in October.

tortugaranger

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PS12B Operating Logic
« Reply #11 on: 18 Sep 2015, 06:54 pm »
Here is the currently conceived operating parameters and control logic for the PS12B. If you have any questions, comments or suggestions I welcome your inputs.
Please note that the PS12B has not been released yet and is still in final development.
__________________

The PS12B is a nominal 12 VDC sealed lead acid (SLA) battery power supply combined with a "smart" charger system. The capacity will either be 5.7 Ah or 7.0 Ah - still finalizing battery selection.

The max current draw is 0.5 A above which a replaceable fuse will blow requiring the unit to be opened up to replace the fuse. The batteries should last for 2-5 year of normal usage, are replaceable and relatively inexpensive.

The objective is for the PS12B to be a hands-off automatic battery based power supply to the Tortuga preamps. Given that the normal current demand of the LDR3.V2 or LDRx is around 135 ma (~200 ma during auto-cal), the PS12B may be able to run the preamp for up to roughly 40 hours (5.7 Ah) to 50 hours (7 Ah) continuously before needing to be recharged. This is a best case scenario and actual time will likely be considerably less. Safe to say, there's more than adequate battery capacity to operate the Tortuga preamps for long listening periods lasting many hours if not all day before needing recharge. Even if almost fully discharged to minimum allowable voltage levels, the PS12B will fully recharge overnight.

The PS12B must be plugged into AC main power at all times in order to operate. The AC mains IEC input socket has an integral 1 A fuse. The PS12B can be pre-configured for either 120 VAC or 240 VAC mains power via an internal set of configurable jumpers.

Summary operational narrative:

The PS12B must be connected to AC main to operate. When not connected to AC main power, the battery output will remain disconnected to prevent over-draining and damaging the battery. In this respect, this is not a portable battery power supply. When connected to AC main power, the default state of the PS12B is for the battery to be connected to the charger and the battery to be connected and available to the user. To use the PS12B to power a Tortuga preamp you'll want to disconnect the charger and run off pure battery power. To disconnect the charger you connect the 12V Trigger out from the preamp to the PS12B. The 12V Trigger out will automatically disconnect the charger when you turn on the preamp and connect it again when you turn the preamp off. This is the preferred "hands off" method. You can also press the push button on the front panel to disconnect the charger. Press it again to connect the charger. If the charger remains disconnected, the battery will eventually discharge to the point where low voltage will automatically disconnect the battery and reconnect the charger. If this happens the PS12B won't be available to power the preamp until it's voltage level is back up above 12.1 volts.

When fully charged, the battery will be at between 13.5 and 14 volts. When voltage drops below 12.1 volts a warning light will come on. When it drops below 11.9 volts the battery will be disconnected and the charger will reconnect to the battery and the battery will remain unavailable until the voltage is back up above 12.1 volts. This automatic shutoff protects the battery from being damaged or shortening its useful life due to over-discharge.

Summarizing the front panel LEDs:

Green/Off - battery disconnected - not available (either because AC mains off or battery voltage too low)
Green/On - battery connected - available

Yellow/Off - charger disconnected
Yellow/On - charger connected to battery and charging battery

Red/Off - battery voltage ok (> 12.1 V)
Red/Blinking - battery voltage getting low (< 12.1 V) and needs charging - time to turn off the preamp
Red/On - battery voltage too low (< 11.9)  - will automatically disconnect battery and turn on the charger

No LEDs lit - means the PS12B is not connected to AC main and the battery is not available

tortugaranger

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Re: PS12B Operating Logic
« Reply #12 on: 19 Sep 2015, 02:17 pm »
Revising the control logic as follows:

Rather than shutting off the battery when voltage falls below a minimum threshold (11.9 volt), the battery will remain connected to power the preamp, however, the charger will be reconnected to prevent further draining of the battery. Under normal preamp load conditions this should prevent further draining of the battery since the charger is designed to deliver more charging current than the preamp draws thus the battery voltage should charge up.

The rationale behind this change is there's a potential downside to simply disconnecting power altogether from the Tortuga preamp while it's turned on and playing music. When power is removed from the LDRs there's a brief period (probably less than a second or so) when the loss of power causes in momentary jump in volume before shutting off. This is largely mitigated in preamps that have input switching but for those that have only a single direct wired input (no input switching relay), this volume surge can be disconcerting. So in an abundance of caution, best to not disconnect batter power and instead just reconnect the charger leaving the preamp powered.

Note, however, the following exceptions:

a) When the PS12B is connected to the preamp and controlled via the preamp 12 Volt Trigger output (the preferred control method), once the preamp is turned off and the 12 Volt Trigger signal goes off, the PS12B battery will also disconnect and remove power to the preamp until such time as the PS12B battery voltage increases to at least 12.1 volts.

b) When the PS12B gets powered up (connected to AC main) and if the battery voltage is below the safe 11.9 volt threshold, the battery will remain disconnected until battery voltage increases to at least 12.1 volts.


Here is the currently conceived operating parameters and control logic for the PS12B. If you have any questions, comments or suggestions I welcome your inputs.
Please note that the PS12B has not been released yet and is still in final development.
__________________

The PS12B is a nominal 12 VDC sealed lead acid (SLA) battery power supply combined with a "smart" charger system. The capacity will either be 5.7 Ah or 7.0 Ah - still finalizing battery selection.

The max current draw is 0.5 A above which a replaceable fuse will blow requiring the unit to be opened up to replace the fuse. The batteries should last for 2-5 year of normal usage, are replaceable and relatively inexpensive.

The objective is for the PS12B to be a hands-off automatic battery based power supply to the Tortuga preamps. Given that the normal current demand of the LDR3.V2 or LDRx is around 135 ma (~200 ma during auto-cal), the PS12B may be able to run the preamp for up to roughly 40 hours (5.7 Ah) to 50 hours (7 Ah) continuously before needing to be recharged. This is a best case scenario and actual time will likely be considerably less. Safe to say, there's more than adequate battery capacity to operate the Tortuga preamps for long listening periods lasting many hours if not all day before needing recharge. Even if almost fully discharged to minimum allowable voltage levels, the PS12B will fully recharge overnight.

The PS12B must be plugged into AC main power at all times in order to operate. The AC mains IEC input socket has an integral 1 A fuse. The PS12B can be pre-configured for either 120 VAC or 240 VAC mains power via an internal set of configurable jumpers.

Summary operational narrative:

The PS12B must be connected to AC main to operate. When not connected to AC main power, the battery output will remain disconnected to prevent over-draining and damaging the battery. In this respect, this is not a portable battery power supply. When connected to AC main power, the default state of the PS12B is for the battery to be connected to the charger and the battery to be connected and available to the user. To use the PS12B to power a Tortuga preamp you'll want to disconnect the charger and run off pure battery power. To disconnect the charger you connect the 12V Trigger out from the preamp to the PS12B. The 12V Trigger out will automatically disconnect the charger when you turn on the preamp and connect it again when you turn the preamp off. This is the preferred "hands off" method. You can also press the push button on the front panel to disconnect the charger. Press it again to connect the charger. If the charger remains disconnected, the battery will eventually discharge to the point where low voltage will automatically disconnect the battery and reconnect the charger. If this happens the PS12B won't be available to power the preamp until it's voltage level is back up above 12.1 volts.

When fully charged, the battery will be at between 13.5 and 14 volts. When voltage drops below 12.1 volts a warning light will come on. When it drops below 11.9 volts the battery will be disconnected and the charger will reconnect to the battery and the battery will remain unavailable until the voltage is back up above 12.1 volts. This automatic shutoff protects the battery from being damaged or shortening its useful life due to over-discharge.

Summarizing the front panel LEDs:

Green/Off - battery disconnected - not available (either because AC mains off or battery voltage too low)
Green/On - battery connected - available

Yellow/Off - charger disconnected
Yellow/On - charger connected to battery and charging battery

Red/Off - battery voltage ok (> 12.1 V)
Red/Blinking - battery voltage getting low (< 12.1 V) and needs charging - time to turn off the preamp
Red/On - battery voltage too low (< 11.9)  - will automatically disconnect battery and turn on the charger

No LEDs lit - means the PS12B is not connected to AC main and the battery is not available

tortugaranger

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Re: Battery Power Supply
« Reply #13 on: 19 Sep 2015, 02:31 pm »
I  am using a specialised audio battery supply for my Tortuga LDR1 ,it is powered by a 12 volt 7 amp sealed lead acid battery (Yuasa).Designed with intelligent charge discharge cycles,and auto cut off when 10.5 v is reached(after a previous low battery warning).I hope to buy a newer model Tortuga soon.Do you know when Tortuga will switch to the newer spec internal power supply more suited to battery use?

http://www.kingrex.com/download/KingRex%20SLAP%20power%20supply%20unit%20-%20user%20manual.pdf

http://www.yuasabatteries.com/pdfs/NP_7_12_DataSheet.pdf

I forgot to mention in my earlier reply that the 10.5 V auto cut off, if that's the correct value, is way too low a level for any sealed lead acid battery. Discharging down to that low a level will permanently damage a SLA battery. Note the discharge table below which is fairly typical of a 12 volt SLA. Anything below a 40% charge (60% discharge) will start to eat into a batteries useful life.

A related anecdote. I recently had a problem with my truck's alternator such that the trucks battery was completely drained 2-3 times over the last 2 months while sitting turned off in the driveway. Killed the battery. Would not hold a charge after that abuse.

 

tortugaranger

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Re: Battery Power Supply
« Reply #14 on: 25 Sep 2015, 02:19 pm »
We've had the Rev 5 prototype board running for several days now going through several cycles of discharge and charge using a simulated load drawing 200 ma and everything is nice and stable and there are no thermal issues. Charging current is limited to roughly 0.5 amp which is more than adequate to recharge the battery from a maximum 50% drained state (11.9 V) back to 100% at 14 volts overnight even when under the 200 ma load.  :thumb:

Looking at the battery DC output waveform, it's dead quiet in the audio band plus out to several 100khz. There's a tiny bit of noise around the 16 megahertz range due to the presence of small microcontroller but that's totally inaudible. However, when the battery is connected to the charger there's a definite ripple in the voltage. The charger wasn't designed to be a low noise DC source so nothing surprising with that.

Based on the Rev 5 results we tweaked the design slightly and expect to have the Rev 6 proto board up and running later today. The Rev 6 board will go to RMAF in the demo unit and barring any surprises will be the final design for the Rev 0 production board. I expect to have production boards in our shop by the end of October. We will probably announce the release date of the PS12B after we get back from RMAF. I'm hoping for a Nov 1 release date. We'll offer it for pre-order at the same time we announce the release date. Pricing is still being finalized but I expect it will be comparable to most other battery based power supplies for audio applications.


To summarize the essential specs the PS12B is a nominal 3.5/7.0 Ah  12 volt sealed lead acid battery power supply with integral smart charger designed to deliver up to 200 ma of ultra low noise DC power for Tortuga preamps and other audio devices. While it can deliver more than 200 ma of current an internal replaceable fuse will blow at 500 ma or if the output is ever short circuited. It uses a fast blow fuse so any short circuit will pop the fuse. The output voltage is unregulated but the PS12B can be optionally equipped with any LM78XX type linear regulator to achieve regulated output.

We've tweaked the operating logic a bit which can be summarized as follows:
  • Upon connection to AC main, charger will connect to the battery and battery output is available.
  • Pushbutton on front panel connects/disconnects the charger as long as voltage is not too low
  • 12 Volt Trigger input to rear panel disconnects the charger when on and disconnects charger when off (overrides the pushbutton)
  • Charger automatically re-connects when battery voltage drops to ~11.9 volts - battery output remains available even when voltage is low. Pushbutton and 12 Volt Trigger input ignored until voltage back up above 12.1 volts (i.e. charger remains connected) and low voltage fault cleared by user via pushbutton.
  • Battery output will automatically disconnect if battery voltage drops below 11 volts (discharging this low will shorten the useful life of the battery)
  • When not connected to AC main there's not way to determine the status of the battery since it will be isolated from both the charger and the output.
Front panel lights:

Blue LED
  • Off - battery disconnected - not available (either because AC mains off or battery voltage too low)
  • On - battery connected - available to power preamp etc.
Green LED
  • Off - charger disconnected from battery
  • On - charger connected to battery and charging battery
Red LED
  • Off - battery voltage ok (> 12.1 V)
  • Blinking - battery voltage running low (< 12.1 V) and needs charging
  • On - battery voltage too low (< 11.9 V) - battery charger will connect automatically
If No LEDs are lit this means the PS12B is not connected to AC main and the battery is not available.


tortugaranger

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Re: Battery Power Supply
« Reply #15 on: 1 Nov 2015, 08:44 pm »
Just a quick update note on the battery power supply. The design is effectively done. I don't anticipate another round of prototype board before going to production. Still deciding on how handle the LED display lights and the front panel. October was a blur not the least because of family health challenges related to elderly parent. I expect to release the PS12 by the end of this month and will start taking pre-orders very soon.

Cheers,
Morten :thumb:

craig sawyers

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Re: Battery Power Supply
« Reply #16 on: 3 Nov 2015, 07:06 pm »
That sounds very exciting Morten - I'll be standing by the credit card!

Craig

tortugaranger

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Re: Battery Power Supply
« Reply #17 on: 16 Nov 2015, 10:03 pm »
Here's a photoshopped mock-up of the front panel of the soon to be released PS12B battery power supply with a LDR3.V2 Passive Preamp sitting on top of it. The main circuit board has been ordered and we're cutting first batch of  front/rear panels later this week.

There are 3 lights plus on pushbutton on the front panel that work as follows:

Power (blue) - indicates whether the unit is plugged into AC main and  turned on  (switch in the rear panel)

Charging (green) - indicates whether the battery is connected to charger circuit. When powering the preamp while it's on the Charger should be off.

Low Bat (red) - indicates when battery level getting low. Blinks when low, stays on when voltage drops below safe level and shuts off power coming out of the power supply.

Charger (pushbutton) - press/release to toggle the Charger on/off


gab

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Re: Battery Power Supply
« Reply #18 on: 16 Nov 2015, 10:38 pm »
a minor critique if you haven't gotten into production yet.

IMO - It would look better if all the silkscreen fonts lined up vertically. This would require the top three to move over to the right just a bit to line up with the "charger" push button. A nit for sure but things like that bother me.  :D

tortugaranger

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Re: Battery Power Supply
« Reply #19 on: 16 Nov 2015, 10:47 pm »
a minor critique if you haven't gotten into production yet.

IMO - It would look better if all the silkscreen fonts lined up vertically. This would require the top three to move over to the right just a bit to line up with the "charger" push button. A nit for sure but things like that bother me.  :D

You are spot on. Noticed that myself after stepping back from it. Fortunately this is just a mock-up. Plus we do our own panel lettering/etching  using a CNC CO2 laser so we have flexibility to fix/modify. Thanks for the critique.