Voodoo Main Discussion

[MartinB]

Ok i have a bunch of wall wart 12 volt different amp chargers a car battery and i also have 6 18650 batteries i wanted to use a 4s at 16 volts then a dc to dc converter to turn it down but i dont have the 4s bms board yet or the converter can i use a car battery or will it not limit the amperage if not ill order the 4s bms board now and the converter

If you are using any mains derived power supply, it must be rated as SELV (Safety or Separated Extra Low Voltage) where the output voltage is totally isolated from the input voltage by means of an isolating transformer. None of the wall warts I have meet this criteria so are not suitable for use. A car battery will give you 12V at up to several hundred amps which could give rise to catastrophic failure if you do not include a current limiting device in your circuit. Best bet is to use 10 X 18650's in a battery holder with short circuit protection. Do not solder them together. Alternatively, use your proposed 4s LIPO and dropdown buck converter which you will be able to reuse in your completed project, but please still incorporate short circuit protection as described by waltr as a shorted LIPO can cause fire and explosion. Make sure you purchase a known brand and not an unbranded cell as these can be unreliable

[SilverSurfer17]

Ok i will hunt down a 40 watt bulb. Ill order the bms also and the converter.

[waltr]

Ok i will hunt down a 40 watt bulb. Ill order the bms also and the converter.

This is a simple automotive tail light bulb. Readily available for a few dollars and can save you many more dollars in blown up parts.
.

[SilverSurfer17]

Yeah i have around 40 of them just in stripped Camaro parts i might even have one on my kitchen table from a golf cart i just rewired for leds ok its just waiting again for parts now thanks guys ill be on standby until i get them

[ionut_mtb]

Came up with these waveforms from Mr DFB setup, now i'm waiting for the uA meter.
Not sure if i need dumping for the Rx or if the sample is in the correct position. Thing is that the sample delay is at max on the right side (100k delay pot max resistance, i tried put 20k series but nothing change)

[Qiaozhi]

Came up with these waveforms from Mr DFB setup, now i'm waiting for the uA meter.
Not sure if i need dumping for the Rx or if the sample is in the correct position. Thing is that the sample delay is at max on the right side (100k delay pot max resistance, i tried put 20k series but nothing change)

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Your DISC sample appears to be in the wrong place. It should be sampling on the ringing part of the waveform after the flyback.

[MartyJ1963]

I just use 3 x 18650 cells which give me 12.6v,,,Why do you need 4 x cells and a converter? Regards, Marty.

[SilverSurfer17]

Im using 12 cells at 16 volts then stepping it down. Because with 3 cells you only use around 30% of the battery. With 4 you use around 40% of the battery. Minus the little you use in the converter.

[SilverSurfer17]

Im also not just using it for my detector. I don't know if you caught my first posts. But I'm building a EV. That i want to be able to mount a bunch of coils on. So i want to be able to charge my phone and gps. The EV will be ran on 72v and i want to keep it separate from my other electronics.

[Matt_Rowe]

Bizzaro world where the positive of a battery is the ground

theres actually quite a few instances especially in the marine industry and boating where Positive grounded systems are the norm. Also especially on some vehicles.

[Matt_Rowe]

Ill just order the 4s and the converter and isolate it from the house ground no biggie i can move around with the detector then anyway ok thank you very much guys much appreciated

you have to use a power supply not connected to your house at all, unless you dont use the neutral or ground, when you have a house current any extra that the device is not using flows back through the neutral wire, back to the utility, and the neutral wire is connected to ground at the service panel.
So you can have current flowing in reverse through your neutral wire into your ground, that is why us electricians always make sure the breaker is turned off before we work on a circuit,In our line of work, the neutral wire is also called a common wire, its named common because its the common test point for all circuits since all neutrals are connected in a house, and neutral gets connected to ground, so actually ground can basically be called a common wire

[Matt_Rowe]

Ok i will hunt down a 40 watt bulb. Ill order the bms also and the converter.

this is how to build a house supply current limiter, for just a few dollars,the plug on the right side of picture is just a standard 2 socket you use in a wall. the light buld could be 20 watt night light, and the light socket is the clay one that gets used in closets, 20 watt still be to much in a MD circuit

[KingJL]

theres actually quite a few instances especially in the marine industry and boating where Positive grounded systems are the norm. Also especially on some vehicles.

Not to show my age... but I remember when our automobile electrical systems was 6V, POSITIVE ground!

[6666]

Not to show my age... but I remember when our automobile electrical systems was 6V, POSITIVE ground!

Yep same here in Oz.

[6666]

Its fairly easy if you have a Pmos, ground is the negative battery plate,
if you have a Nmos ground is positive battery plate.
If you have a a virtual ground (or virtual earth) then thats a little different,
usually made from a couple of resisters or an op amp with the node as ground.

Whats being proposed with the current limiting is a simple 12 volt globe in series with the load powered from the 12 volt side of the power supply which is isolated from the mains.
I just use an 8 pack of nicads.