Servo size, distance of operation and reliability of throw.

Dave S
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Re: Servo size, distance of operation and reliability of throw.

#11

Post by Dave S »

Thank-you Roger and TDD. Duly noted. Nice to know you find the hardwear reliable.

>I did try coding my own controller but got intermittent twitching issues.
Painful! :shock:

That reminds me of when I was about 6 and had a shock from a transformer cable on the 240v side at my mates house.
Burnt a layer of skin off my hand.
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Brian
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Re: Servo size, distance of operation and reliability of throw.

#12

Post by Brian »

My MERG Servo controllers don't cause a twitch!..
But as a DCC user I do ensure the Servo leads are kept away from the DCC Bus pair of wires as much as practical and the servo leads are only ever extended by around 400mm. If longer is ever needed I then use a new servo driver board. A MERG kit for a CBUS (2 wire overall operation control system) with 8 outputs is just £14.69 That is £1.83 per output! Or for a conventional directly switch operated servo board, for four Servos its currently just £4.93 or £1.23 per servo output. OK I do acknowledge you have to be able to solder components correctly onto a circuit board and also have to become a MERG member. But IMO that annual membership fee (£16) out ways anything commercially sold and the back up from fellow members is exceptional!
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Dave S
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Re: Servo size, distance of operation and reliability of throw.

#13

Post by Dave S »

I have noticed the cables only tend to be sold in lengths of 10 or 20cm, maybe that's why.
Though I assumed these (branded Dupont on ebay) also carry data to/from servo board back to central contoller/switch, that could be several metres.
Are longer cables available or is it a case of cutting each cable in half to add extra length in the middle?
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teedoubleudee
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Re: Servo size, distance of operation and reliability of throw.

#14

Post by teedoubleudee »

I have used extension cables up to 2m without issues.

This site sells up to 3.5m though they are currently out of stock of the longer lengths.

https://www.ebay.co.uk/itm/331683590534 ... 0809611290
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teedoubleudee
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Re: Servo size, distance of operation and reliability of throw.

#15

Post by teedoubleudee »

I recommend using servo cable locks like these when extending servo cables:

https://www.ebay.co.uk/itm/163144887950 ... BM3ICazM1f
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Dave S
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Re: Servo size, distance of operation and reliability of throw.

#16

Post by Dave S »

Thank-you TDD, I did look for a while without luck.
Still in planning stage, but nothing beats foresight. ;-)
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RogerB
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Re: Servo size, distance of operation and reliability of throw.

#17

Post by RogerB »

Many moons ago the MegaPoints chap put a video up on his website [which seems to have been removed] demonstrating servo operation over a cable several 100 feet in length with no noticeable latency. R-
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teedoubleudee
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Re: Servo size, distance of operation and reliability of throw.

#18

Post by teedoubleudee »

RogerB wrote: Tue Jan 18, 2022 11:27 am Many moons ago the MegaPoints chap put a video up on his website [which seems to have been removed] demonstrating servo operation over a cable several 100 feet in length with no noticeable latency. R-
Obviously there will be a drop in signal levels over longer lengths due to the resistance of the wire being used, but the bigger problem as I understand it, is electrical "noise" or interference from nearby electronic devices, as mentioned earlier by Brian. It's a bit like running loud speaker cables next to mains cables and picking up the 50 Hz hum from them.

Those youtube vids from Dave at Megapoints are quite informative about using his products.
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Dave S
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Re: Servo size, distance of operation and reliability of throw.

#19

Post by Dave S »

On a sliight tangent, but still relating to servos...
Live frog wiring.
I've used peco insulfrog in past and checking out live (or unifrog) it seems that although the point blade can pass the current to frog, it is better to wire up the frog seperately, with polarity changed on point throw.
The example had a peco point motor with spare terminals for this.
If using servos, do they have the same capability, so having extra terminals that can throw 12V to the frog?

All the servos i've seen tend to be 5V, so would assume, even if they had this extra capability, they can only throw 5V output.
I'm planning on using arduino type boards to drive the servos, so is there an alternative way, with cable from arduino board to frog...but that would still only be 5V.
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Re: Servo size, distance of operation and reliability of throw.

#20

Post by teedoubleudee »

Servos do not have any switching ability but you have a couple of choices. First you can use the movement of the servo to switch a separate micro switch. Some servo bases cater for this.
Secondly, as you are using a micro computer to drive the servo you can also drive a relay at the same time.
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