Things getting hot.

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Paulmchurd
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Things getting hot.

Post by Paulmchurd » Thu Mar 01, 2018 5:00 pm

I’ve been messing around with some electronics but I can’t figure out what is going on and if it is normal. Tried to google my questions but can’t find any forum posts similar.

I’ve hooked up a 180mah 3s lipo to a 3A esc to a 6v n20 motor.

I understand I’m over vaulting the motor however the motor is not over heating and is still working. The ESC is getting hot though.

Is my battery giving out too many amps and overheating the esc or are there to many vaults being sent to the motor, can’t go any where and over heating the esc?

Also when an esc says it can handle 3A. Is that talking about the current coming from the battery through the esc, stalling of the motor or neither?

Thanks
Confused Paul

**EDIT**

Found something on the web. It said over vaulting a DC motor generates heat. Which has to go somewhere. Which is usually the wires. That will then transfer into the esc. Is this correct and what my problem is?

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MarkR
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Re: Things getting hot.

Post by MarkR » Thu Mar 01, 2018 5:16 pm

You can measure the current by putting a multimeter in series with the circuit. Alternatively one of those wire-clamp current measurement thingies will do too.

It's normal for some types of electronics to get hot. If the ESC is rated for the voltage and current you're using, it should be no problem. Some of them are cooled by assuming they're in a RC plane with air constantly flowing over a heat sink though.

Another possibility is that some of the wiring is a bit high-resistance for the application. You can measure the resistance of the wire (possibly), check the wire gauge or solder joins.
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Paulmchurd
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Re: Things getting hot.

Post by Paulmchurd » Thu Mar 01, 2018 5:27 pm

That’s a good idea. I don’t have one unfortunately:(

It’s a FingerTech tiny esc btw.

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Re: Things getting hot.

Post by Paulmchurd » Fri Mar 02, 2018 6:00 pm

Borrowed a multimeter...

The motor is giving off 0.02A continuous and 0.4A stall. It’s a 3-6V rated motor. My conclusion is there is voltage left over which just ends up turning into heat. I could test this by adding in a variable resistor to absorb the unused voltage.

Wish my 12v rated motors would hurry up and arrive in the post...

Wish I’d done things like this at school... so much more interesting then light bulbs in a circuit.

Did I just think aloud?

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Shakey
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Re: Things getting hot.

Post by Shakey » Fri Mar 02, 2018 6:23 pm

Paulmchurd wrote:
Fri Mar 02, 2018 6:00 pm
The motor is giving off 0.02A continuous and 0.4A stall. It’s a 3-6V rated motor. My conclusion is there is voltage left over which just ends up turning into heat. I could test this by adding in a variable resistor to absorb the unused voltage.
That's not how it works, you don't get 'voltage left over'. Think of a circuit like a bit of plumbing. How fast the water flows is current (A), how much flows is power (W), how much force is behind the water is Voltage (Or Push), how easy a bit of pipe is to flow through is resistance (Ohm).

The motor is always using that full voltage but for its resistance only that 0.4A is flowing through it. A 3A rated ESC means it is simply fine to have 3A move through the ESC, less just means an easier time for the ESC. A 3-6V rated motor simply means it is designed and safe to run normally at 3-6v. Running it on 12V doesn't mean there is voltage left over, it means the motor is going to consume more current (And therefore power) and may be operating outside of its safe limits.

A 3A ESC should have absolutely no problem with a 0.4A motor, that is spades of room for it to be happy in, you could pack another 6 motors on and stall them and in theory it should be happy and fine. However it may be a bad quality ESC with shoot through (current essentially skipping the motor and flowing inside the ESC generating heat) or a poorly specified BEC (The ESC has parts of itself that want a lot less voltage so a voltage regulator may be used, this effectively wastes power to limit what voltage the sensitive gets and as a byproduct makes heat, normally this is fine. Sometimes it's done badly and at higher voltages is having to create more heat to protect the ESC).

"Is my battery giving out too many amps and overheating the esc or are there to many vaults being sent to the motor, can’t go any where and over heating the esc?"
Voltage is pushed, Amps are drawn. This means the voltage is pushed by the battery to everything else but the circuit decides how much current is taken from the battery. Think of your house, it is connected to the national grid and in doing so is connected to dozens of power stations across the country completely capable of providing enough current to render it a small smouldering ruin, but it is fine as it only takes what it needs current wise.
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Re: Things getting hot.

Post by Paulmchurd » Fri Mar 02, 2018 10:36 pm

Ahhh I think I understand all that.

The heat is generated because the BEC only needs 5v and the way the ESC reduces the voltage is by creating heat as a by product?

Or the current is skipping the motor and going directly into the esc. I could test this by putting the amp meter between the battery and esc?

Thanks for the help. I was writing down my thoughts trying to find answer. This hobby is new to me.

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Re: Things getting hot.

Post by MarkR » Fri Mar 02, 2018 11:23 pm

"BEC" is a weird term invented by RC people for a voltage regulator. In the electronics world they are generally referred to as regulators.

There are two types of regulator - linear and switching. Linear regulators work, as you say, by conceptually dumping some amount of virtual resistance into the circuit to reduce the voltage - this wastes a proportion of the power depending on exactly how much voltage is dropped; obviously more power used = more power wasted. Switching regulators work by rapidly turning on and off the supply to keep a capacitor charged to the correct voltage; these are efficient but the switching introduces electrical noise which might interfere with other stuff.

However the regulator should not be getting really hot if you're only using it to drive the RX. As far as I understand it, many speed controllers provide a regulator (aka BEC) output, because they need an onboard regulator anyway for the chips they use onboard to drive the motors and/or decode the pwm.

I plan to use the Dasmikro (speed controller) regulator to drive a Raspberry Pi Zero, I've no idea if it will even work or if I will break it. I hope not.
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Shakey
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Re: Things getting hot.

Post by Shakey » Fri Mar 02, 2018 11:53 pm

I'd be amazed to see a hobby 3A ESC with a switching regulator.

In any case I'm putting this down to the voltage drop being too great for its reg to handle cleanly or a straight up poor quality ESC (Hell why not even a poor quality reg!). It's not totally abnormal for some ESCs to barely handle their own draw, these things are built for max profit with every penny saved. Shoot through is gonna be tricky to pick up on a normal multimeter and tell it apart from general power consumption of the ESC itself. It's extremely small spikes during the switching of the FETs which are happening thousands of times a second and then those peaks hidden by the caps.

For an actual fix I can recommend the Vex29 range of brushed ESC's (with cases removed). They are single channel, bi directional, £9 and robust as hell. Americans use them for beetle motors up to 4S (with some reports of 6S, their voltage rating is heat based not absolute).
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Re: Things getting hot.

Post by Paulmchurd » Sat Mar 03, 2018 12:10 am

Shakey wrote:
Fri Mar 02, 2018 11:53 pm
I'd be amazed to see a hobby 3A ESC with a switching regulator.

In any case I'm putting this down to the voltage drop being too great for its reg to handle cleanly or a straight up poor quality ESC (Hell why not even a poor quality reg!). It's not totally abnormal for some ESCs to barely handle their own draw, these things are built for max profit with every penny saved. Shoot through is gonna be tricky to pick up on a normal multimeter and tell it apart from general power consumption of the ESC itself. It's extremely small spikes during the switching of the FETs which are happening thousands of times a second and then those peaks hidden by the caps.

For an actual fix I can recommend the Vex29 range of brushed ESC's (with cases removed). They are single channel, bi directional, £9 and robust as hell. Americans use them for beetle motors up to 4S (with some reports of 6S, their voltage rating is heat based not absolute).
The problem is it’s not actually a cheap ESC. It’s a FingerTech Tiny ESC. Supposedly able to handle 36volts. That why I was surprised it got hot and decided to hit the forums to find out why.

Hopefully I’ve not fallen for a sales technique of our esc can handle everything to splash my cash.

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Re: Things getting hot.

Post by GeorgeR » Sat Mar 03, 2018 6:23 pm

The fingertech is a good quality esc, and I'm sure it can handle the voltage. My initial hunch is that you might be drawing too much current on the bec line.

What was the full setup? So which receiver were you using and did you have any other esc's or servos attached?
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Re: Things getting hot.

Post by voorsk » Sat Mar 03, 2018 6:52 pm

closest experience i have is fixing zx spectrums.. after the modulator bypass, the next job was always to replace the voltage regulator, as the old ones were incredibly inefficient. if you remember the 128k 'toastrack', that whole 6 inch heatsink was for the voltage regulator, dropping 9v to 5v!

that probably doesn't help, does it? I'm probably just showing my age. :p
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Paulmchurd
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Re: Things getting hot.

Post by Paulmchurd » Sat Mar 03, 2018 8:15 pm

GeorgeR wrote:
Sat Mar 03, 2018 6:23 pm
The fingertech is a good quality esc, and I'm sure it can handle the voltage. My initial hunch is that you might be drawing too much current on the bec line.

What was the full setup? So which receiver were you using and did you have any other esc's or servos attached?
I’m using this Rx https://hobbyking.com/en_us/turnigy-ia6 ... eiver.html

N20 motor, 3s 180mah galaxy lipo tiny esc and that Rx.

No servo or other esc.

I didn’t know what a voltage regulator was voorsk untill I started building robots. Haha!

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Re: Things getting hot.

Post by Paulmchurd » Sun Mar 04, 2018 11:06 am

I think i managed to hook up the multimeter to check the current draw to the Rx.

It registered 0.15A the esc BEC says it can handle 0.1.

I’ve ordered a micro BEC that can handle 1A which cost £2.50! I can do some testing and hopefully that will solve the over heating problem.

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Re: Things getting hot.

Post by GeorgeR » Sun Mar 04, 2018 12:55 pm

Looks like you found the problem, the specs on that receiver say it should draw 30mA (0.03A), so it seems its pulling a lot more power than it should. Also the fingertech bec is actually only rated at 40mA with a 12v supply (100mA is for less than 8V) so it would definitely get hot running 150mA.

The separate 1A because should solve your problems, just remember to disconnect the bec wire from the fingertech.
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Re: Things getting hot.

Post by Paulmchurd » Sun Mar 04, 2018 1:27 pm

Ahhh I was wondering what the graph meant. Seems the Rx could be faulty. I have a second one. I’ll test it to see what it’s current draw is.

**EDIT**

Tested second RX. This one is pulling 0.06A. Even that is too much.

Thanks for the help everyone. I enjoyed the problem solving but couldn’t have done it with out this forum.

Paul

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