Servo Tester

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Rob

New Member
#2
#2
Have built servo tester cicuit as shown - only action is for the servo to twitch when power switched on, cannot see any real reason why wont work - ideas anyone?
 
K

Konrad

Member
#3
#3
Hi Rob,

I haven't built this circuit yet so I can't comment on the circuits efficacy. I do have some experience of using servos in radio controlled models, both aircraft and cars. Whenever I have experienced servo twitch it has been caused by some form of interference, not necessarily from your circuit but signals from things like refrigerators and the like when tested indoors and in close proximity. The servo tends to glitch and twitch if their is a fault in the rx. Sometimes the servo itself can be faulty. Try another servo. My bet is that its noise from either external components or maybe the circuit itself. I have had to install ceramic capacitors to small electric motors before now to cut the excess noise that can affect a servo. That's my best guess, hope it helps or at least points you in the right direction.

Konrad :)
 
R

Rob

New Member
#4
#4
Konrad said:
Hi Rob,

I haven't built this circuit yet so I can't comment on the circuits efficacy. I do have some experience of using servos in radio controlled models, both aircraft and cars. Whenever I have experienced servo twitch it has been caused by some form of interference, not necessarily from your circuit but signals from things like refrigerators and the like when tested indoors and in close proximity. The servo tends to glitch and twitch if their is a fault in the rx. Sometimes the servo itself can be faulty. Try another servo. My bet is that its noise from either external components or maybe the circuit itself. I have had to install ceramic capacitors to small electric motors before now to cut the excess noise that can affect a servo. That's my best guess, hope it helps or at least points you in the right direction.

Konrad :)
Click to expand...
Konrad - thanks for the thought, but I am an experienced RC aeromodeller and in fact used to own my own model shop. I can guarantee that it is not IF causing the twitch which is exactly the same as when most standard RC RX's are switched on. I am at a loss as to next move, I do know how to handle IC's but this is my first use of a 555 and need someone to point me in a likely direction - please note I have a scope available so can check on what really should be happening.
 
K

Konrad

Member
#5
#5
Hi Rob,
I think this will be my next build. Perhaps you can help me with a question I have regarding the circuit. Into what and where exactly do you plug the servo connector? From my experience these can be of a slightly different design, so one plug does not fit every rx. Surely you don't have to take the plug of the servo to get it into the circuit. Perhaps I'm missing something from the schematic. A case of 'can't see the wood for the trees'.

Konrad :confused:
 
R

Rob

New Member
#6
#6
Konrad said:
Hi Rob,
I think this will be my next build. Perhaps you can help me with a question I have regarding the circuit. Into what and where exactly do you plug the servo connector? From my experience these can be of a slightly different design, so one plug does not fit every rx. Surely you don't have to take the plug of the servo to get it into the circuit. Perhaps I'm missing something from the schematic. A case of 'can't see the wood for the trees'.

Konrad :confused:
Click to expand...
Hi Konrad - I used a female connector from an unused servo extention lead - simply cut the lead in half and soldered the lead into the respective holes on my circuit board, (please note you can buy female only leads from the better model shops or one of the bigger electronic suppliers), I simply had a lead handy. You are correct saying that there are differences in some servo connections - if you are using either Futaba or JR compatible leads then the circuit shows the correct layout black(brown)= neg. red=pos. white(yellow, orange)=signal. The positive is usually the centre lead in a flat cable. Also the JR and Futaba plugs are not physically identical even though they are electrically the same. I remove the small ridge on a Futaba plug carefully, it will then fit either system and you only have to make sure that it's the right way round! A few of the less popular brands use all black leads, personally I refused to stock these when I had my shop as they were more prone to problems - the only reliable way to check these black leads is to look at the same manufacturers RX and note which lead is which. Finally, if you haven't got a suitable lead, then providing you are happy to remove the servo plug, simply solder the leads directly into your circuit.
 
K

Konrad

Member
#7
#7
Hi Rob,
Agree with everything you said. Looking more closely at the schematic I decided to add the flying leads to the circuit where shown and simply 'poke' the other ends into the plug on the servo, this way you can test any make of servo immediately and without any fuss regarding pin configuration and plug design. All you have to do is make sure the three leads correspond with the correct holes on the servo plug being tested.
I have put this circuit together but it's not working. When I connect the battery the servo output arm moves slightly in one direction and does so everytime you make and break the connection. The problem is the push switches do not have any effect and the BC547 transistor gets very hot very quickly. I have tried a number of configurations regarding the layout of the switches for forward/reverse but nothing solves the problem. The good thing about using a breadboard is that changes can be made very quickly and components can be used repeatedly.
Have you had any success yet? Perhaps you could post a photo of your circuit and we could compare what we have done. As I said before the sticking point for me is the layout of the two switches, the rest of the circuit seems straightforward enough.

Konrad :eek:
 
K

Konrad

Member
#9
#9
Another go at the servo tester circuit this time with partial success. See photo attached. The servo output arm rotates one way when power is applied to the circuit but the switches have no effect on the circuit. Has anybody built this circuit and had complete success? Perhaps admin (phil) could comment on my layout and tell me where I have gone wrong. Once again the switches seem to be the problem.
thanks,

Konrad:(
 

Attachments

R

Rob

New Member
#10
#10
Konrad
Rob here - I have tried several fresh attempts at building this circuit - still no luck, all components have been either checked or replaced so no dud ones, there is obviously something critical in the circuit, I would have expected something to happen - but zilch! Agree would ADMIN come to the rescue.
Rob
 
K

Konrad

Member
#11
#11
Hello Rob,
I agree, it would be very helpful if admin commented on this circuit. I have already posted a pic of my breadboard layout and this should be easily digested and commented on. Better still would be one of the super duper breadboard layouts he has posted on other circuits.
Konrad :(
 
Justin

Justin

Member
#12
#12
Konrad said:
Hello Rob,
I have already posted a pic of my breadboard layout and this should be easily digested and commented on. Better still would be one of the super duper breadboard layouts he has posted on other circuits.
Konrad :(
Click to expand...

Hey Konrad, I took your advice and made a breadboard layout based on this circuit diagram. I haven't reviewed it 100% so there may be a mistake; if there is and you happen to spot it, please let me know so I can fix it A.S.A.P.

I also made a Microsoft word document that contains both the circuit diagram and the breadboard layout in a neat, two page, file that is ready to print. This file is availbe online and you can download that here.

I also made the Servo Tester Remote breadboard layout based off this circuit diagram. It is also inside the Microsoft Word Document.

 
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Konrad

Member
#13
#13
Unfortunately when I try and open the document mentioned above all I get is a page of undecipherable gobbledygook. Even station X would be struggling to decipher. LOL.
Konrad :eek:
 
Justin

Justin

Member
#14
#14
Konrad said:
Unfortunately when I try and open the document mentioned above all I get is a page of undecipherable gobbledygook. Even station X would be struggling to decipher. LOL.
Konrad :eek:
Click to expand...
That's odd? I just tried it and it work fine. It doesn't really matter though because it just had the breadboard layouts and the circuit diagrams found on this site. I haven't the slightest clue as to why the link doesn't work.
 
Justin

Justin

Member
#15
#15
I've updated the links, try now Konrad.
I've updated my breadboard layout

I also made a Microsoft word document that contains both the circuit diagram and the breadboard layout in a neat, one page, file that is ready to print. This file is availbe online and you can download that here.
 
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