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Brownout Step Up Converter
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ceengland7(at)gmail.com
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PostPosted: Sat Sep 26, 2020 12:28 pm    Post subject: Brownout Step Up Converter Reply with quote

Additional thought. Did you ensure that your bench power supply was supplying the additional current needed when the voltage drops? Mine has a current limit knob in addition to the voltage control; I have to be sure I've dialed in enough current that the supply doesn't hit the limit.

Charlie

On 9/26/2020 2:29 PM, Charlie England wrote:

Quote:
I re-ran the test, dialing back to as low as 7V as quickly as possible while using the pot on the power supply. No difference in characteristics. 


I then tried it with the lamp fed only by the booster; same result. At 7V supply, current demand is a few tenths over the 4A rating of the booster, and output voltage dropped to right at 10V. Below 7V the booster seems to shut down (light slowly goes out) and if V is brought back up to ~12V, it recovers within a second or two. Remember, I'm recording data with Mk1 eyeball & pencil. I'll report again when I get it 'breadboarded' in the plane.


What's the exchange rate & border penalty in Canada these days? I paid less than US$8 for the pack of 5, shipped. (Sincere apologies if you're getting Trumped.)


Charlie


On Sat, Sep 26, 2020 at 12:44 PM Sebastien <cluros(at)gmail.com (cluros(at)gmail.com)> wrote:

Quote:
Very interesting Charlie. I was only using a 1A automotive bulb for load and as you say my converter looks like it's using the same hardware as yours so maybe the addition of the second power path makes enough of a difference? I would not have thought so but it's worth a try, I'll wire it up again and see. 

Also when dropping the voltage down to 8V I'm doing it as quickly as possible with the power supply fine adjustment. Were you slowly decreasing the input voltage or doing so suddenly?


Mine was $10 CAD for one and those ones are $30 for 5 so the price is ok.


On Sat, Sep 26, 2020 at 9:55 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

Quote:
Hi Sebastian,


Thought I'd share some rough testing on a 4A rated booster, that seems to use the same inverter IC as the one you're using. I bought these:
https://smile.amazon.com/gp/product/B07XG323G8/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I used an automotive brake light bulb that measures 2A draw at 14V and ~1.8A at 12.5V (about what a tired battery might be).



My results with the booster in the circuit, set for 11V output, which should be adequate to keep an EFIS alive. 
(list is: supply V/A    booster V): 


14/2.1  12.6
12/2.0  11.1
10/2.7  11.1
9/3.1  11.1
8.5/3.6  11.0
8.0/3.4  10.5
Supply V/A are read off my cheap Asian variable supply display, and rounded to nearest tenth. Booster output V measured with Fluke meter, rounded to nearest tenth.
After several minutes with the supply at 8V, the booster output starts dropping a bit. I suspect that is because the inverter IC has no heat sink and is beginning to thermal-limit to protect itself. In any case, the booster should be loaded for only a few seconds during the start event.


Note: One thing I did was to insert a 'fat' diode in series with the supply that goes directly to the lamp (also shown in the Z figure). The diode output and the booster output both feed the lamp. When supply voltage drops below booster output, the diode prevents the booster trying to feed back into the supply at the booster's set voltage (obviously impossible).


Did you check your battery voltage at the battery terminals, or were you using the EFIS to monitor battery voltage? My experience is that depending on how the a/c is wired, the EFIS may see a lower than actual voltage, due to diodes (or resistances) in the path to the EFIS input. Battery voltage dropping to the 6V area when starting sounds like either high resistance in the battery circuit, or a tired battery.


My GRT EFIS has multiple diode-isolated inputs, so the next step is to wire the booster from my E-bus to a spare power input on the EFIS & try it out.


Charlie


On Sat, Sep 19, 2020 at 11:36 AM Sebastien <cluros(at)gmail.com (cluros(at)gmail.com)> wrote:

Quote:
Now I'm getting confused. The converter Bob linked to has a minimum of 10 volts input. Charlie's is 8.5 volts. The only time we want these units working is below 10 volts, and they need to work much lower than that. The last start on my aircraft recorded a 7.6 from a fully charged battery and that's just what the EFIS managed to capture at 1 sample per second.

Looking again I have found a couple units that claim to work at very low voltages:


https://www.ebay.ca/itm/DC-DC-10A-Buck-Boost-Converter-Step-Up-Down-regulator-Module-for-LED-Driver-US/254169431168
https://www.ebay.ca/itm/DC-DC-Buck-Boost-Converter-Adjustable-CC-CV-Step-Up-Down-Power-Supply-Module/124260980594


I'm considering ordering one for further testing.


Bob best wishes for a quick recovery but take your time. Get yourself fully in fettle before worrying about anyone else!




On Sat, Sep 19, 2020 at 8:17 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

Quote:
On 9/19/2020 9:26 AM, Robert L. Nuckolls, III wrote:

Quote:
At 11:02 PM 9/17/2020, you wrote:
Quote:
A couple weeks ago I ordered one of these off eBay:

https://www.ebay.ca/itm/192243452240

DC-DC Converter
5 Amps
Input 3-35 V
Output 5-40 V

I'm trying to support ~1 A EFIS during start so I thought 5 A would be plenty but a closer look at the description says it's good for 3 A with a maximum of 5 A. Turns out the 3 A is on the input side, not the output side. With a voltage output set point of 10V and a ~1 A lamp connected, the lamp browns out (literally) as soon as the input voltage sags below 9V. A long way from the 7V minimum I was hoping for. I plugged it into a Battery Analyzer at 1.0 and 0.5 A and momentarily dropped the input voltage to 8V. Even when voltage is restored it takes several seconds to recover back to the set voltage with a 1 A load. A 0.5 A load is fine.

  Good investigative work sir!  You're
  on the right track. The up-converter
  you have is a bit on the light side.

  I'd go for beefy . . . and the up-converter
  needs to be characterized in Watts.  A converter
  that would support a 5A load at 14V would be
  rated at 70 W or more.

  The test articles I have on hand are, as I recall,
  150 W devices. I'm hoping to put power to them
  to see if I can characterize their dynamic qualities
  before I send you one.

  I'm a bit out of pocket right now. Getting ready for
  some roto-rooter work on my back . . . got a leg
  that occasionally says, "I quit". It would not be
  a good thing to be loading a patient and suddenly
  find yourself on the ground asking the patient
  to help you up!

  Doc says it's a quick fix with excellent
  prospects for success but in the interim,
  my forays about the shop are limited. The
  up converters I have are, I believe, this
  one:

https://tinyurl.com/yxndk24a

  Price is right, size is convenient . . .
  and there is little risk for having
  one that is too big. Thanks for sharing
  your observations.



  Bob . . .
These:
https://www.ebay.com/itm/DC-DC-Converter-10-12-15-20A-150-250-300-400-1200W-Step-up-Step-down-Buck-Boost/382219150784?hash=item58fe0965c0:g:6OwAAOSwisVZrgue
Claim to be good down to 8.5V input. Various wattage versions available.

Charlie

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