Esc power safety switch?

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jhsa
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Re: Esc power safety switch?

Post by jhsa » Mon May 05, 2014 9:55 pm

I wonder if the push button and the LED should be on a separate little PCB. I will probably donate this one to one of the guys at the field. He flies with the stock 9x and the stock RF module.

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Re: Esc power safety switch?

Post by gohsthb » Mon May 05, 2014 9:58 pm

I think depends on how it mounts in the plane. Maybe if those were the only 2 parts on that side of the board, they could stick out enough to go through the fuselage.

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jhsa
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Re: Esc power safety switch?

Post by jhsa » Mon May 05, 2014 10:24 pm

Yeah, but that means a real PCB ;)
Maybe the attiny can be soldered on the copper strips side. I was going to put also an smd low drop voltage regulator, but I thought that for testing a through hole 78L33 would be ok. We should keep it quite easier to build. That means big ;) :D

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ShowMaster
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Re: Esc power safety switch?

Post by ShowMaster » Thu May 08, 2014 9:45 pm

Did we decide the ATtiny circuit is the one to try? I'm reading up on programming it. Not something I've done. I have the UNO and found this explication of programming.
http://m.instructables.com/id/Program-a ... h-Arduino/
I should have ITtiny's from past programming attempts. What's the number of the smallest one that will workI? 've got to look for them in the to do before I die project box.




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jhsa
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Re: Esc power safety switch?

Post by jhsa » Thu May 08, 2014 11:42 pm

Attiny 25, 45, or 85. default fuses.
To program them you might want to try "AVR Burn-O-Mat". It is a GUI for Avrdude.
If there is nothing on the programmers list, make sure the path to avrdude.exe and avrdude.conf is correct. after change it, restart the program.
This program works very well with stk500 compatible programmer, but it doesn't want to read the chip with my usbasp. it doesn't like it.. Me neither :)

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Re: Esc power safety switch?

Post by gohsthb » Fri May 09, 2014 2:00 am

I've been using my avr Dragon for programming mine. But you can use any isp type programmer. The usbasp should be fine. Check the data sheet for the attiny25 to see where the different connections go. And don't forget a 0.1uF across 5v and ground. If you do use a usbasp make sure it is one where the speed can be changed. To test your connections use the avrdude command line:
Avrdude -c usbasp -P usb -p attiny25 -B 10 -v

-B 10 you know changes the speed, because the tiny will be running at 1MHz
-v will print out more information so you can see it worked

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ShowMaster
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Re: Esc power safety switch?

Post by ShowMaster » Fri May 09, 2014 3:52 am

Thanks guys for the tips. I think I have one USBasp programmer that's had the FW flashed to let me change settings.
The rest are older HK versions.


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The Easy Way

Post by Flaps 30 » Tue May 13, 2014 12:17 pm

Further work was done on Skynorth's original idea. My initial changes worked fairly well, other than when the LED was changed to a high brightness one I could see a dim glow from it. So the change was to remove two resistors and the bipolar transistor, replacing then with a nice FET. The FET used (BS270) is one that gets used here a lot as it doesn't switch on until the gate voltage gets above one Volt and in this case that is important as the voltage on the gate gets no lower than 0.75/0.8 Volts when the FET should be off. The workhorse 2N7000 has a minimum voltage of 0.8 Volts which is too close for comfort so it isn't really suitable for use in this circuit. You could replace the BS270 with a 2N7002 if you so wish as the Vgs low threshold is the same.
ESC_Safe Mod mosfet Final.gif
This circuit is easy to make and it drives a high brightness LED nicely. No software to mess with or horrid little chips or components to solder onto as you can use real old fashioned stuff and chunky (up to 1mm) lumps of solder to glue it all together. :)

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Re: Esc power safety switch?

Post by jhsa » Tue May 13, 2014 12:36 pm

Yeah, it is easier to build as it doesn't need any programming, but I do like some features from Gohst's project with the attiny.
It only arms if the throttle is at idle. this one will send the motor spinning if the stick is not at idle. Also to disarm you must have another button?
The one with the micro also has failsafe in case of using receivers that stop the pulses when the link is lost. but most esc's also do that. Actually, this needs to be reviewed, I just thought of something. If the link is lost the attiny will disarm but I guess if the signal returns it will remain disarmed? and that is not ideal? :) Gohst, what do you think?? Maybe in case of link loss force the PWM to say -100 without disarming? Or is it what it already does?
Other than that, as long as it saves some fingers, one or the other.. :)

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Re: Esc power safety switch?

Post by gohsthb » Tue May 13, 2014 1:01 pm

If the Rx has failsafe it should kick in before the attiny times out and sees a signal loss (This needs to be tested, does the Rx keep sending pulses until the failsafe engages? or does it stop for a while? How long?). The the attiny will not disarm itself, as it sees a continuous stream of pulses. On a Rx without failsafe, and that stops sending pulses, it will disarm itself and stay that way. I was trying to avoid sending pulses to the ESC. I like carrying my aircraft out, and then arming the ESC. Just seems a bit safer to me. Sending -100 will arm the ESC. It's not only up to me though, I like other peoples input.
-Gohst

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jhsa
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Re: Esc power safety switch?

Post by jhsa » Tue May 13, 2014 1:21 pm

The problem is that if losing link in flight and then recover, as some spektrum equipment like to do, ;) the esc will be disarmed and force the plane to an unpowered landing.. also after the loss and possible recovery of link you might need immediate power to save the plane in case the signal comes back..
I saw something similar happening with the taranis at my field. The guy was pointing the antenna at the aircraft and the receiver's failsafe kicked in for a while. Obviously he hadn't configured it and the plane kept all channels at middle point/last position. Throttle included. Lucky that I was near and screemed at him to turn the antenna. We had just spoken about it before his flight and I told him not to point the antenna at the model, to which he replied that there is no problem doing that.. Surprise, surprise... :D

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Re: Esc power safety switch?

Post by MikeB » Tue May 13, 2014 1:22 pm

At the cost of a couple more resistors, you could add a potential divider in the gate circuit of Q1. This could drop the gate voltage by a couple of tenths of a volt when off, but should still allow enough voltage to turn on.

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Bill
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Re: Esc power safety switch?

Post by Bill » Tue May 13, 2014 1:57 pm

At the risk of stating the obvious again the whole point of this would be to make the motor safe before and after flight. You need to be able to disable the motor after flight as or before you pick it up.
Flaps 30's circuit doesn't do this, why do you need to be responsive to lack of signal the ESC itself deals with that at least all the ones I've ever had do.
The important thing is to have reliable disablement and you know its disabled a toggle switch!!
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Re: Esc power safety switch?

Post by jhsa » Tue May 13, 2014 2:06 pm

with the toggle switch, you forget to put the throttle at idle before you arm it and you might be in for a painful surprise ;) that is why it is not that simple in my opinion.. But that is not the point. we are offering several solutions for the problem. the switch is obviously one of them.. People can choose which one to build.. ;) The attiny is the safest. The switch not so safe in my opinion and the other circuit is somewhere in the middle.. :D

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Re: Esc power safety switch?

Post by Bill » Tue May 13, 2014 8:45 pm

On all the escs I have the throttle will not respond unless it's taken to the low throttle position first, just like when you turn it on, if you initially power them up at anything other than low throttle they don't start.
What is required in MHO OK MO is a 100% cut off that doesn't reset itself due to power fluctuations and maybe a LED a double pole single throw switch. :roll:
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Re: Esc power safety switch?

Post by Flaps 30 » Wed May 14, 2014 12:01 am

Mike - Yes that would do it. The divider on the bipolar version was the cause of the changes. Given that there is now an FET in place now, it would be possible to add a high value divider as the input Z of the FET is high. It's just that I have a lot (like a couple of hundred) BS270's in my junk box that are ideal for interfacing with logic devices or in situations like this one.
Bill wrote:What is required in MHO OK MO is a 100% cut off that doesn't reset itself due to power fluctuations and maybe a LED a double pole single throw switch. :roll:
Yup - Agreed on that. Don't forget to add a resistor in series with the LED to the +5 Volt line to limit the current. Instead of a double pole toggle switch that could be accidentally knocked on or off (unless it is the locking variety) how about using a 3.5mm stereo jack plug and socket arrangement. Removing the jack plug arms the motor. Don't forget the obligatory fluorescent red tag that should be attached to the jack plug saying something like "Remove before flight to arm motor" just in case you or someone else forgets to do it. :)

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Re: Esc power safety switch?

Post by jhsa » Tue Feb 23, 2016 11:18 pm

I have built one of Gohsthb's ESC Safe with an Attiny85 for a friend of mine.

João
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Re: Esc power safety switch?

Post by gohsthb » Wed Feb 24, 2016 4:11 am

Wow, I forgot I even wrote this. If you want the source it should be available here: https://docs.google.com/document/d/19zd ... cslist_api

It looks good on a board!
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jhsa
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Re: Esc power safety switch?

Post by jhsa » Wed Feb 24, 2016 8:12 am

Thank you.
I had a friend of mine visiting me the other day and apparently his radio can't do a sticky Thr cut. So I've decided to build a couple for him. :)

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