Your Thoughts On This Wiring Diagram

[RotorJockey]

... Another thought from my previous post: for every contact, be it switch or relay, introduced in the line applies a small series resistance, therefor a loss of power (applied voltage) to the device.

Prove this by accurately measuring the voltage at the battery and the voltage at the device. This difference voltage (in fraction of Volts) ÷ Current flow in Amps = the equivalent resistance of all the contacts in the circuit.

You'll be surprised!

 

[AzViper]

Negative! ('scuse the pun).

A circuit consists of two wires. Switching either would produce a spark. The switch rating is (say) 200-Amps - that means, once closed, the metal parts in the switch can 'handle' that current. The same as when touching two connectors together, the switch metal will spark as the two parts touch, eventually burning away the contact(s). Even then, the switch introduces a small value of resistance in circuit, causing heat losses.

The current (at time of contact) will be in the order of thousands of amps. The capacitor 'sucks' the current according to 'little-r' (or Equivalent Series Resistance) in the order of 25 milli-Ohms. Applying Ohms' Law - Amps = Volts ÷ Resistance. Substituting: 40V (6S) ÷ 0.025 Ohms (say) = 1600 Amps (for about 20 milli-Seconds, until the capacitor(s) charge up)!

Even a large arc-welder would do well to reach this level. The figures above are representative, but give the idea.

You have to introduce a current limiting fixed resistor temporarily in series with the (+ve or -ve) lead to lower the charging current, and allow the time for the capacitor(s) to fully charge; then 'short-out' this resistor to allow the circuit to draw the required current to operate efficiently. Remember that a circuit (device) draws current relative to the applied voltage and the resistance (impedance) of the device.

Capacitors are a virtual short-circuit over the battery until charged.

This Is The (Physical) Law ...

Contacts are designed for thousands of operations. I work with loads of 1000's of amps were the contacts are open and closed a few hundred times per month over a period of years.

 

[RotorJockey]

That is so. There are contacts and there are contacts.

The ones you mention will definitely not fly! I'm thinking of those you would use in an MR.

 

[AzViper]

... Another thought from my previous post: for every contact, be it switch or relay, introduced in the line applies a small series resistance, therefor a loss of power (applied voltage) to the device.

Prove this by accurately measuring the voltage at the battery and the voltage at the device. This difference voltage (in fraction of Volts) ÷ Current flow in Amps = the equivalent resistance of all the contacts in the circuit.

You'll be surprised!

Then your statement then holds true for every solder joint, every bullet connection. However you want to look at at every connection between the battery and it's components is an opportunity for failure. It's a risk ever time the craft is put in the air.

 

[SJBrit]

Then your statement then holds true for every solder joint, every bullet connection. However you want to look at at every connection between the battery and it's components is an opportunity for failure. It's a risk ever time the craft is put in the air.

Which is precisely why to take every measure you can to reduce the risks, including omitting redundant connections. When you add risk (connections) you really ought to have a good reason which takes me back to my question that you've never actually answered: what problem are you trying to solve?

 

[AzViper]

Which is precisely why to take every measure you can to reduce the risks, including omitting redundant connections. When you add risk (connections) you really ought to have a good reason which takes me back to my question that you've never actually answered: what problem are you trying to solve?

I never mention I was out to solve a problem, but I did answer why I was exploring this idea that so many are against on page two of this thread. Many of you are so dead set it will not work yet none of you have tied, yet even with the bullet connections you still have to physically bring the positive and negative together to make a connection and what takes place the very split second?

 

[SJBrit]

I never mention I was out to solve a problem, but I did answer why I was exploring this idea that so many are against on page two of this thread. Many of you are so dead set it will not work yet none of you have tied, yet even with the bullet connections you still have to physically bring the positive and negative together to make a connection and what takes place the very split second?

At that very split second my anti-spark bullet places a 5 ohm resistor in series to massively reduce startup current and completely eliminate any sparking. Then I push the bullet fully together and the resistor is bypassed as the main current carrying part of the bullet mates. It's quick, easy, reliable, cheap, light - pretty good deal.

Try not to take all this the wrong way - we are truly trying to help. Either you are a pioneer breaking new ground that none of us has considered, or someone with little experience posting a thread asking for advice from people who have built multirotors before. We're just trying to point out that most people use a simple mechanical connection, and pretty much all of those people have heard of relays.

Here's an irrefutable fact: any mechanical connector subjected to large instantaneous current will spark when you make the connection unless a small resistor is placed in series. Here's another fact: sparking will build up carbon deposits over time and even erode the metal connector. Both add resistance and resistance = losses in the form of heat. Do some reading: people have built up enough resistance in well worn connections to create enough heat to desolder the connector in flight. The advice here is not to knock down your ideas but to try to warn you of the consequences of not taking steps to avoid sparking.

You may or may not wish to take our advice (which you asked for) but please don't be mad with us for giving it.

 

[AzViper]

My entire point is that a mechanical relay will work and without sparking provided if it's designed correctly, yet everyone is saying it will not work.

The above post just reinstated stated my point. I appreciate everyone's concerns and again I am not against the bullets, but wanted to throw out that there are other means of arriving without sparking when a connection is made.

I will admit I am new to multirotors but not new to R/C. My first thread was to gather information on the components cause I did not understand how all the components worked with each other.

 

[AzViper]

Ok I will admit this is a simple connection using the bullets and most likely the direction I will go but...

 

[SJBrit]

Ok I will admit this is a simple connection using the bullets and most likely the direction I will go but...

And they are even easier once the outer casings are screwed on.

 

[SJBrit]

My entire point is that a mechanical relay will work and without sparking provided if it's designed correctly, yet everyone is saying it will not work.

The above post just reinstated stated my point. I appreciate everyone's concerns and again I am not against the bullets, but wanted to throw out that there are other means of arriving without sparking when a connection is made.

I will admit I am new to multirotors but not new to R/C. My first thread was to gather information on the components cause I did not understand how all the components worked with each other.

Just to round out the discussion: nobody is saying that a relay won't work, just asking: why bother? And the relay will spark - any electrical conductors brought into close contact and trying to pass high current will spark. The only way to stop a spark is a current-limiting resistor. If you do go the relay route you should either think about how to mimic the momentary resistor circuit that the bullet connectors achieve, or try to choose a relay contact material that will still work with high DC inrush currents, like silver-tin-oxide or silver-tin-indium. They don't prevent sparking but they do hold up fairly well.

 

[AzViper]

Just to round out the discussion: nobody is saying that a relay won't work, just asking: why bother? And the relay will spark - any electrical conductors brought into close contact and trying to pass high current will spark. The only way to stop a spark is a current-limiting resistor. If you do go the relay route you should either think about how to mimic the momentary resistor circuit that the bullet connectors achieve, or try to choose a relay contact material that will still work with high DC inrush currents, like silver-tin-oxide or silver-tin-indium. They don't prevent sparking but they do hold up fairly well.

Again I know your protecting others as my drawing was crude drawing. I have said if the circuit is designed correctly. Nobody is to follow the drawing without knowing firsthand what to buy and how to design a non sparking relay on closure. Your directing your statement at me as if I don't know how to place the relay in use without sparking.

 

[SJBrit]

Again I know your protecting others as my drawing was crude drawing. I have said if the circuit is designed correctly. Nobody is to follow the drawing without knowing firsthand what to buy and how to design a non sparking relay on closure. Your directing your statement at me as if I don't know how to place the relay in use without sparking.

Yes, exactly. It's always good to remember that these threads live on as reference sources for people so if you do go the relay route I think it would be great to post up your solution for others to follow if they want.