Help needed -faulty rx channel?

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Walcal
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Joined: Sat Aug 20, 2016 3:41 pm

Help needed -faulty rx channel?

Post by Walcal »

Hi folks, new here and to botmaking. Thanks for having me.

Upon the arrival of the new Robot Wars I felt inspired to take on my first ant build, and I'm the final stages of wiring it up, but have encountered a problem I can't seem to decipher with my receiver/servos.

I'm using a Fly Sky FS-GT2B with accompanying FS-GR3E 3 ch receiver. The ant is servo driven with a servo powered flipper (. Channels 2 and 3 work perfectly, with channel 2 being a wheel and 3 being the flipper. However, channel 1 is giving me problems. Upon connecting up a fresh servo and turning the system on, it appears to sync up like the other two, but doesn't respond to commands from the controller. Upon connecting a modded servo, the shaft just continually rotates, while also ignoring commands, but this does point to the battery, a 3.7v 380mah lipo, being capable of powering everything. Binding doesn't seem to solve the problem.
I can't think of anything causing the problem other than the battery not providing enough voltage to send the signal? Do I simply need a new battery?
Any advice on batteries and such or alternative solutions would be greatly appreciated.
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BeligerAnt
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Re: Help needed -faulty rx channel?

Post by BeligerAnt »

If you are using a 3.7V (single cell) battery, then that's your problem.
I don't know your receiver but Googling for the spec indicates that it runs on 4-11V. Unless you have very tiny servos they probably also expect 5V or so.

Apart from needing more volts you also don't need anywhere near 380mAh capacity. A 7.4V (2 cell) 180mAh will probably be smaller and lighter and will definitely work a lot better for you.

You can test the theory if you have some AA batteries handy. 4 in series will give you 6V and will happily run an antweight for ages (apart from the weight issue ;) ) and allow you to check that everything's working properly.
Gary, Team BeligerAnt
Walcal
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Re: Help needed -faulty rx channel?

Post by Walcal »

The servos I'm using are micro 4.8-7.2v. I have been tempted by a lot of 7.4v battery options but I'm worried about my servos.
Thanks for the advice on the amperage. I do have actually have a battery holder that could work for the time being. However I have already found out that any size of AA battery pack I have may cause weight/space problems, so I'm stuck looking for a solution for the finished ant.
Can I risk going .2 over the volt limit on the servos? I'm not sure I'm keen on spending a servo to find out...
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peterwaller
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Re: Help needed -faulty rx channel?

Post by peterwaller »

Although they quote 2 cell LiPo's as 7.4 V they are in fact 8.4 V fully charged so there could be a risk using them directly on to the servo's.
There are other options.
Small NiMh come in many options such as 1/4 AAA 120maH
http://www.ebay.co.uk/itm/361177767031? ... EBIDX%3AIT
or 1/2 AAA 210 mah
http://www.ebay.co.uk/itm/121077676041? ... EBIDX%3AIT
or use a BEC to give you 5V regulated supply from the 2 cell Lipo such as below although I have never tried these particular ones.
http://www.ebay.co.uk/itm/2-6S-Lipo-BEC ... SwuMFUdtAp
Walcal
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Re: Help needed -faulty rx channel?

Post by Walcal »

I hadn't thought of using a BEC like that, sounds like just the thing I'm after. I'll note down the other options as well. Thank you for the suggestions.
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BeligerAnt
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Re: Help needed -faulty rx channel?

Post by BeligerAnt »

Since the receiver works off 4-11V and most servos won't cope with much more than 6 or 7 volts (certainly not 11!) the receiver probably includes some sort of BEC/regulator to power the servo outputs. Whether it can provide enough current to reliably drive 3 servos may be an issue though...
Gary, Team BeligerAnt
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UserFriendly
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Re: Help needed -faulty rx channel?

Post by UserFriendly »

Could you use something like this :
https://www.pololu.com/product/2123
It's a step up voltage regulator , so you could supply 5v to your servos from your 1S, 3.7v batt?
Once you've confirmed with the aa batteries that voltage is the problem, perhaps look for something like this. You can probably get one cheaper than Pololu.
Andy B - Team UserFriendly
Reading Cybernetics Graduate 1996
Trying not to take Antweights too seriously. I think I'm failing.
First AWS was 46.
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