[TriEmbed] Powering ESP32 from an 8v golf cart battery
Josh Wyatt
dragojdw at gmail.com
Thu Nov 19 14:42:35 CST 2020
You know, now that you mention it, I have a bunch of DC-DC boards as well,
buck converters, LM2596S based, they are not the most efficient but great
for prototyping; both voltage and current limited separately adjustable, if
anybody needs one. Vin 4.5-40VDC, Vout 3.0-36.5 VDC, Iout max is
(optimistically) 3 amps, if this would be useful.
-j
On Thu, Nov 19, 2020 at 3:07 PM Nick Edgington via TriEmbed <
triembed at triembed.org> wrote:
> I also have in my box of stuff a number of *ARTESYN NFC40-48T05-15 in
> DC/DC 36-72V 5V at 7.5A& +-15V at .75A
> <https://pdf1.alldatasheet.com/datasheet-pdf/view/156797/ARTESYN/NFC40-48T05-15.html>*
> isolated DC-DC converter modules, most forklifts and golf carts seem to
> run 48v, they have never been used and are a little overkill here, I had
> bought them for a POE project If they would help you are welcome to one.
>
> Nick
>
> On Thu, Nov 19, 2020 at 2:37 PM John Wettroth via TriEmbed <
> triembed at triembed.org> wrote:
>
>> Pete,
>> If the high current peaks are a small fraction of the time, you can
>> "bypass" your way around it- I don't know if the ESP gadgets do this- maybe
>> you or others do.
>>
>> There are several systems that do this in either simple or pretty complex
>> ways. We called these techniques "BFC" for big fat capacitor.
>>
>> If you have a high current spike that is drawn for some time at some
>> current- the product iT is charge- coulombs. Charge is also CV, so you can
>> charge up a cap and dump into your load. The simplest way to do this to
>> have big cap at the load fed by a low value resistor to limit recharge
>> current to something you can live with. If the duty cycle is low, you
>> can blast out a big pulse and then have plenty of time to charge back up
>> before its needed. The problem is usually that in this simple case, you
>> need to use a much larger cap 10x than just CV would dictate because while
>> the cap is discharging- the charge is depleting and its voltage is
>> falling (I/c =dv/dt). To limit the droop to something liveable, you uses
>> an 8x or 10x sized cap- this way it only droops 10 or 12% over the burst.
>>
>> The first time that I ever saw this trick was in two way pagers way back
>> when. The reciever on a pager drew nothing but when 2 ways came out, every
>> now and then, they needed to send a little text message and that drew a
>> bunch of current. This was the techniuque. In two way pagers, they
>> engineered in the droop and started with transmit power kind of dialed back
>> and as the cap discharged, it turned up the relative power in order to keep
>> a constant total power output. Pretty clever, this was early days of
>> supercaps but they were high impedance, the newer ones would be great- like
>> from Maxwell. I think they just used a few thousand uF tantalum or some
>> kind of nice electrolytic like a Sanyo OS-Con.
>>
>> There are quite a few systems that use this trick- I've seen a lot of
>> hobby (and pro) spot welders that do this. A lot of energy harvesting
>> systems take in energy as the can until they get enough and then do their
>> high powered thing and start the cycle again. Walmart had these little
>> solar powered LCD price tags (about 2 x 1" cell) that worked this
>> way. The host system had IR emitters in the ceiling that sent command to
>> the tags. The tags could always receive but they communicated
>> acknowldgements back to the system with an IR led when they could. The
>> time budget was something like an hour or something- better than sending a
>> person with a price gun etc.
>>
>> I saw a fancier system at Rockwell Automation- AKA Allen Bradely. A
>> common problem in industrial is "last gasp" mode on power failures. In
>> these little PLC's they need to shutdown in an orderly way and it took
>> someting like a minute. Batteries weren't an option in most cases due to
>> life. They came up with a clever little discrete circuit using maybe 4
>> transistors and an inductor. It consited of a boost converter that took
>> the 24v and made something like 300v to charge a HV cap. The same little
>> circuit could turn around and become a buck converter that could take the
>> 300v and bring it back to 24v when the power failed. This takes a
>> different tack and uses a pretty nice bit of physics. The energy in a
>> capacitor is 1/2 CV^2, by boosting up the voltage they could get this
>> squared energy. Energy is Power x Time, (watt-seconds or joules). When
>> the engineer showed me his solution, I was amazed and we couldn't make
>> anything any cheaper or better really.
>>
>> I guess the ultimate in this is Xenon flash strobes though I don't think
>> phones have to rely on this for using LED flash- the battery has such a low
>> impedance, you just hammer it for a little bit.
>>
>> I have a little Ryobi cordless nailer- I don't know exactly how it works
>> but the final action is a piston that runs from an air resevoir. I don't
>> know if it has a little tiny air compressor that fills up the air resevoir
>> or some kind of piston run by solenoid to recharge the air. It
>> recycles really quickly. There is a tear down by AVe on the web. I need
>> to watch it again.
>>
>> If you know the peak current, duration, etc- you can see if this works
>> for the ESP32. The charge storage IT is good but the energy storage with
>> the 1/2CV^2 with a buck boost could work probably. I would think that a
>> regulators like Nick found would be simplest- its kind of ideally suited
>> excecpt for the 5v max Vin.
>>
>>
>>
>> Regards,
>> John M. Wettroth
>> (984) 329-5420 (home)
>> (919) 349-9875 (cell)
>>
>>
>> ------------------------------
>> *From:* TriEmbed [mailto:triembed-bounces at triembed.org] *On Behalf Of *Pete
>> Soper via TriEmbed
>> *Sent:* Thursday, November 19, 2020 10:47 AM
>> *To:* triembed at triembed.org
>> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>>
>> Thanks for sharing, this, John. The other day trying to gauge how much
>> Paul's golf cart battery would be drained with a linear vs switching
>> regulator a very quick glance of ESP32 stuff gave a guestimate of about
>> 4.7V*50mA (but I guessed this wasted power wasn't relevant to Paul). But I
>> hadn't thought at all about peak currents as they relate to regulator
>> choice, and more importantly how much time is spent at those higher
>> currents.
>>
>> But I'm writing to wonder how much help decoupling the regulator and
>> minimizing inductance might help with transient scenarios like you describe
>> below? Or would the cap dumping current just fake out the regulator and
>> simply make the droop happen a little later?
>>
>> -Pete
>> On 11/19/20 8:53 AM, John Wettroth via TriEmbed wrote:
>>
>> That's a nice part Nick. Like a lot of modern parts on small process,
>> its kind of designed around one LiIon cell operation. I like the "green
>> mode" stuff. LTC and Maxim make some parts like that. The difficulty with
>> switchover type parts is when you have a big load transient (eg- a transmit
>> burst). If the part is in the low quiescent mode, it can droop and cause
>> havoc.I noticed it has a forced green mode pin which could alleviate this
>> with some thought in software. A lot of times, its easier to have a
>> seperate regulator for the high current case or if they can be split up.
>>
>> I didn't realize that these ESP devices require so much current, I've
>> only played with one on the bench pretty casually. For the 8v input case,
>> you really might want to consider a buck converter unless the high current
>> only runs very intermittently. The power wasted in a linear could create
>> potential heat problems. You're talking about getting rid of 1.5 watts
>> from your 8v source.
>>
>> I agree with Nick on those DFN packages- awful, you're into hot air or
>> oven reflow. I like parts that come in a variety of packages including
>> through hole, this is getting rare these days.
>>
>> Regards,
>> John M. Wettroth
>> (984) 329-5420 (home)
>> (919) 349-9875 (cell)
>>
>> ------------------------------
>> *From:* Nick Edgington [mailto:nickedgington at edgingtonlabs.com
>> <nickedgington at edgingtonlabs.com>]
>> *Sent:* Wednesday, November 18, 2020 6:44 PM
>> *To:* Josh Wyatt
>> *Cc:* jwet at mindspring.com; TriEmbed Discussion
>> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>>
>> personal I like the STM *LD39130SJ30R*
>> <https://www.st.com/resource/en/datasheet/ld39130s.pdf>which is a good
>> match for esp32 it will do 300ma with a 300mv drop the quiescent current is
>> a remarkable 1 µA in green mode, 45 µA in normal mode which matched with
>> the ULP mode on the esp32, Not a problem with a golf cart but important
>> for low power sensor. and to top it of STM will send you a couple for just
>> the shipping cost,
>>
>> The package a somewhat of a pain.
>>
>> Nick
>>
>> I have a number of the regulator board I pictured earlier should you be
>> near Apex and want one.
>>
>>
>> nje
>>
>> On Wed, Nov 18, 2020 at 1:17 PM Josh Wyatt via TriEmbed <
>> triembed at triembed.org> wrote:
>>
>>> This is awesome info John, I'm enjoying the read.
>>>
>>> From personal experience, the ESP32S (and ESP8266) can be pretty power
>>> hungry when the radios are on, and are particularly sensitive to
>>> brownouts... I try to use something with at least 300mA and with good,
>>> stiff caps.
>>>
>>> Thanks,
>>> Josh
>>>
>>> On Wed, Nov 18, 2020 at 9:42 AM John Wettroth via TriEmbed <
>>> triembed at triembed.org> wrote:
>>>
>>>> Shane,
>>>> There are a ton and its unfortunately one of these "it depends" kind of
>>>> things. But here are a few and why.
>>>>
>>>> Most of the stuff I do is pretty small, low current stuff and 2.7 or
>>>> 3.3v- an 8 bit uP and a display with some RF. Very low quiescent
>>>> parts suitable for circuits with sleep mode, etc. A lot of my stuff lives
>>>> outside and runs on a 12v battery so I try to shoot for -40C operation and
>>>> 16v Max vin. Temp range matters for capacitors mostly and dropout. I buy
>>>> almost exclusively from Digikey. Their search engine and service is
>>>> amazing even if they cost a bit more. I tend to design very low power
>>>> things and like low Iq for sleep operation. Generally very low Iq means
>>>> poor HF rejection (you need loop gain)- in RF stuff, I'll compromise on Iq
>>>> and shut the block down, etc. I prefer newer parts, there has been so much
>>>> progress in the last 15 years, its amazing- there is no reason to use a
>>>> 7805 for any real design- even cheap stuff. There are better and even
>>>> cheaper alternatives if you're building more than a few hundred. At low
>>>> volumes, 7805's can be awfully cheap but they're really only designed as
>>>> 60/120 Hz type regulators in a traditional AC supply.
>>>>
>>>> Some old favorites-
>>>>
>>>> Micrel (Mchip owns Micrel linear now) MIC5203, 5205 series of BiCMOS
>>>> types. PNP pass element but controlled drop out current. 16v 50/150 mA,
>>>> Iq 1 mA max. Micrel invented BiCMOS pretty much and its good to see that
>>>> Microchip is keeping a lot of their parts.
>>>>
>>>> Microchip 1791 is a great HV regulator- 30v max in, 70 mA out, load
>>>> dump (48V), Iq 70 uA. Microchip makes tons of cheap analog parts these
>>>> days and lot of good linears. They acquired Telcom semi many years ago
>>>> which was a big CMOS linear company (like Maxim). Newer CMOS stuff is good
>>>> but the older stuff is not so good- done on large processes and traded Low
>>>> Iq for performance- very slow load and line transient recovery, no PSRR,
>>>> etc.
>>>>
>>>> Toko TK11625 and TK1150, Digikey dropped Toko but I still have a lot of
>>>> these around- they're officially obsolete but they're plentiful everywhere
>>>> and there are newer alternatives. Available in TO-92, 100 mA, Tk71150 is 5v
>>>> LDO with good HF rejection for low noise for a post after a switcher,
>>>> Quiescent is OK at 300 uA, Seiko makes similar BiCMOS parts, can be hard
>>>> to find these days. Microchip basically copied these regulators to create
>>>> their line and DigiKey wants to keep Mchip happy.
>>>>
>>>> TI TLV1117 A "special" very low Iq LM1117 variant, quiescent of 100
>>>> uA. Better PSRR and dropout. Good in 3 Alkaline of 1 LiIon to 2.5v apps.
>>>> Max Vin is 5.5v, only downside.
>>>>
>>>> Some favorites lately (doing low cost stuff)
>>>>
>>>> Diodes Inc AP-7381 series. Available in TO-92 option still for quick
>>>> perfboard builds and breadboard. Cheap. Very low Quiescent, 50/150
>>>> mA variants. Digikey large stocks always.
>>>>
>>>> ABLIC S-812Cxx series. 1uA Iq, 10-100 mA output depend on voltage.
>>>> Quiescent useful for running a real time clock or deep shutdown on a HV
>>>> input.
>>>>
>>>> Anything that Maxim or LTC/ADI makes are invariably awesome but low
>>>> volume pricing (<10k) is awful. Real customers pay nothing like those
>>>> prices believe me. I have odds and ends of Maxim leftovers but never have
>>>> what I need. TI has better pricing but isn't innovating much in this area-
>>>> the TLV1117 is an exception- excellent.
>>>>
>>>> In your Golf Cart app, what's your load current min and max and vin min
>>>> and max. Any big line or load steps? Temp range and size could help too.
>>>> Any special operation needs like sleep?
>>>>
>>>> After 25 years in Standard Products at Maxim, I can talk Linear IC's
>>>> more than anyone cares to listen. Take care- shoot me a private mail or
>>>> call if you have specific questions.
>>>>
>>>> Regards,
>>>> John M. Wettroth
>>>> (984) 329-5420 (home)
>>>> (919) 349-9875 (cell)
>>>>
>>>>
>>>> ------------------------------
>>>> *From:* Shane Trent [mailto:shanedtrent at gmail.com]
>>>> *Sent:* Tuesday, November 17, 2020 9:57 AM
>>>> *To:* jwet at mindspring.com
>>>> *Cc:* Pete Soper; TriEmbed Discussion
>>>> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>>>>
>>>> John,
>>>>
>>>> Thank you for your breakdown on voltage regulators. Would you mind
>>>> sharing some of your favorite part numbers in the "Modern BiCMOS LDOs"?
>>>>
>>>> Thanks!
>>>> Shane
>>>>
>>>> On Mon, Nov 16, 2020 at 5:52 PM John Wettroth via TriEmbed <
>>>> triembed at triembed.org> wrote:
>>>>
>>>>> I'll put my 2 cents in here for a few subtleties. I defined
>>>>> probably 1000 different linear and switching regulators at Maxim in my 25
>>>>> years.
>>>>>
>>>>>
>>>>> Vout plus dropout is pretty good overall. But don't forget that
>>>>> dropout is defined where the output voltage drops 100 mV. Its coming out
>>>>> of regulation and all the goodness that linears give you stops happening.
>>>>> You also want to do this at max load, max output tolerance and worst temp.
>>>>> The drop out for bipolars decreases for higher temps which helps but at
>>>>> very cold temps, it can grow- a lot a very cold. This is not allways well
>>>>> specified.
>>>>>
>>>>> There are several classes of dropout that are driven by the design of
>>>>> the ouput stage
>>>>>
>>>>> Vdropout
>>>>>
>>>>> 2v standard bipolar linears like the 7805 use an NPN darlington
>>>>> output- nice low impedance and easy to use.
>>>>> 1v LM1117 type bipolar linears use a Sziklai modified darlington
>>>>> with an NPN follower driven by a PNP- pretty good comprimise
>>>>> .5v LM2940 PNP pass element parts have low dropout but some
>>>>> squirelly stability issues at times and can have high quiescent at dropout
>>>>> .1v PMOS or charge pumped NPN pass element types that looks like a
>>>>> small resistance in dropout. Quiescent can be very low.
>>>>> .
>>>>> Depending on the type of regulator, there are subtlties that happen
>>>>> around dropout.
>>>>>
>>>>> Old bipolar regulators like the 7805 have a drop out of about 2v
>>>>> conservatively. The output is an emitter follower darlington stage which
>>>>> is 2 vbe's (.7v each) and 2 Vce sat (about .2v each). This is about 1.8v.
>>>>> Since the output is a follower, it has a gain of 1 and are generally very
>>>>> well behaved with very little thought given to bypassing and stability.
>>>>> High frequency rejection is poor and accuracy is somewhat poor.
>>>>>
>>>>> First generation bipolar LDO's like the LM2940 etc, used a PNP output
>>>>> stage with a grounded NPN pulling its base down. These parts have two Vce
>>>>> sats in the dropout path (about .5v). These transistors have gain on top
>>>>> of the error amp gain and get unstable without following the the bypassing
>>>>> instructions closely. The output cap becomes the dominant pole and the ESR
>>>>> of the output cap has to in a specific range- neither two small or two
>>>>> large. The other annoying feature of this class is as you approach
>>>>> dropout- the beta provided by the PNP pass element goes south and they can
>>>>> draw lots of current at or near dropout trying to keep the PNP in
>>>>> saturation. In low power circuits, this can cause a sort of latching
>>>>> action and flatten a battery in no time.
>>>>>
>>>>> The LM1117 type second gen bipolar LDO's have a NPN follower ouput.
>>>>> These have the benefit of a follower but only moderate dropout
>>>>> performance. They were basically invented to make 3.3v from 5v which a
>>>>> 7805 couldn't do. Good for point of load but kind of mediocre otherwise.
>>>>>
>>>>> Modern BiCMOS LDO's generally have a PMOS pass element and some MOS
>>>>> and Bipolar circuits.. These can have very low quiescent, very low noise
>>>>> and the lowest dropout possible. They are also pretty stable with most
>>>>> loads but take a signicant cap on the output usually. Something like a 10
>>>>> uF ceramic. Microchip make some good low cost parts in this class.
>>>>> Probably my favorites.
>>>>>
>>>>> There are all CMOS LDO's that share most of features of the last
>>>>> category but don't get the low noise and high accurancy generally.
>>>>>
>>>>> One other issue is your 8v battery. The charging voltage on a Lead
>>>>> Acid could be over 10V which is a common abs max for many linears.
>>>>>
>>>>> My 2 cents.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Regards,
>>>>> John M. Wettroth
>>>>> (984) 329-5420 (home)
>>>>> (919) 349-9875 (cell)
>>>>>
>>>>>
>>>>> ------------------------------
>>>>> *From:* TriEmbed [mailto:triembed-bounces at triembed.org] *On Behalf Of
>>>>> *Pete Soper via TriEmbed
>>>>> *Sent:* Monday, November 16, 2020 10:46 AM
>>>>> *To:* triembed at triembed.org
>>>>> *Subject:* Re: [TriEmbed] Powering ESP32 from an 8v golf cart battery
>>>>>
>>>>>
>>>>> On 11/15/20 10:34 PM, The MacDougals via TriEmbed wrote:
>>>>> _______________________________________________
>>>>> Triangle, NC Embedded Computing mailing list
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>>>>>
>>>>
>>>> --
>>>> [image: photo]
>>>> *Shane D Trent*
>>>> Patent Agent
>>>>
>>>> 919-348-0061 | shanedtrent at gmail.com
>>>>
>>>> ShaneTrent.com | Skype: skype:shane.trent1
>>>> <#m_4537398578539011642_m_4427072674128384416_m_133033098193379331_m_189338381597980778_SignatureSanitizer_SafeHtmlFilter_>
>>>> Raleigh, North Carolina
>>>> [image: Social icon] <http://www.linkedin.com/in/shanetrent> [image:
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>>>>
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