I kinda of favor the pcb solution, if you have time. A small board in shrink wrap should work nicely. Do you use Eagle for your layouts? I would be happy to help with layout and checking, if needed.

Holes can be drilled without a drill press. If you can get the cheap phenolic board, not fiberglass, your drills will last much longer. Just use a HSS (preferred) or other steel bit, not carbide. I have done it with the bit held in a pin vise and rotated it with my fingers. There are not that many holes to drill.

John

 

Me again. I haven't yet been able to use my PCB as I haven't got access to a suitable drill press or drill bit so no progress on that front.

I've attempted a circuit I found here on allaboutcircuits
http://forum.allaboutcircuits.com/showthread.php?t=35692

Again, i've exactly the same problem. The circuit does absolutely nothing whatsoever. I am getting really frustrated trying to see where i'm going wrong but I just can't pinpoint where i'm going wrong with this supposedly simple circuit.

I'm starting to think it may be just my breadboard layout but even as to that I can't see where I made a mistake.

 

BREAKTHROUGH!!!!

It seems the 555 timer has actually begun to work! I now get a constant sound from the servo and the potentiometer actually has an effect on it. The sound can only be described as something you'd hear from a 56k modem. Now it appears that my problem has moved from the servo not receiving any signal to the servo receiving an incompatible signal.

 

I've uploaded a video to show you what I mean.
http://www.youtube.com/watch?v=XVtba1gSZAE

Ok perhaps the potentiometer does not have any effect. I've just removed it to see if it made any difference and it appears that that sound is being caused by something being wrong before the pot.

Could it possibly be low voltage? What appears to be wrong?

 

Your new circuit is identical to the old circuit with exception of the capacitor on pin 5 that doesn't matter and different component values. I don't know whether the new values give the proper timing or not.

The big question in my mind is why did you change them at all? The old values were just fine, except for changing the 3M3 resistor.

I was a bit bored so I redrew the schematic and made a very rough PCB to show it can be done without jumpers. Do not make that PCB as is. It was done just to find an acceptable component placement. The airwire is ground and would be replaced by doing a copper pour.

John

View attachment 26711

View attachment 26712

 

What is the supply voltage? It must be in the range of 4.5V - 15V for the NE555. You look like you are using 4xNiMH or NiCd which gives 4.8V nominal, if they are flat expect much less. It could also be that 4.8V isn't enough to run the servo. Can you measure the pack voltage?

 

The breakthrough was actually on the old circuit. Well old component values more like considering both circuits are the exact same. Any idea what could be the issue with my current breadboard setup considering the video? I'll more than likely end up ordering SMD components and making it on PCB directly considering you've tested it and know that it works. But even so it'd be nice to have it working on breadboard first.

 

What is the supply voltage? It must be in the range of 4.5V - 15V for the NE555. You look like you are using 4xNiMH or NiCd which gives 4.8V nominal, if they are flat expect much less. It could also be that 4.8V isn't enough to run the servo. Can you measure the pack voltage?

4 x Alkaline which aren't much better. I'm going to see if I can find a 6v transformer lying around and i'll splice the lead and use it as a power supply.

 

4 x Alkaline which aren't much better. I'm going to see if I can find a 6v transformer lying around and i'll splice the lead and use it as a power supply.

I'm guessing you don't have a scope?

 

I'm guessing you don't have a scope?

You guessed right

I used to have a multimeter lying around but that seems to have disappeared. If I had an OSC and a multimeter my life would be much easier.

 

Model servos run perfectly well on 4 NiCd or NiMH batteries. John

 

Ok i've managed to analyse the situation a bit further. It appears that it's receiving a signal past it's range in the clockwise direction. My reasoning behind this is that if I manually move the servo back to it's anticlockwise limit upon plugging it back in it moves smoothly back to its clockwise limit. So it appears that that whining sound i'm hearing is actually the servo reaching its clockwise hardware limit. So from this I can say that it's operating at the correct signal rate but the signal is out of range.

Any ideas on how I would go about changing the range? Currently i've a 560r resistor leading up to the pot from pin 1 and two 3m3 resistors in parallel connected to pin 7 and the other pins.

 

I'm going to order SMD components this weekend to make the PCB. I just have a quick question. I can desolder and solder SMD components fairly well by hand but it's quite a lot of bother and to do it well it would take an awful lot of time that I do not have. I have access to a vacuum forming machine which has an infrared heater. Forgive me if i'm wrong but couldn't I simply place the PCB on the stage covered with some solder paste and then just have the components pulled in to perfect alignment by surface tension?

And I still haven't given up on getting it to work on the breadboard so if anyone has anything to say with regard to that, let me know.

 

Jpanhalt, could you help me out with drawing up a circuit layout if I showed you the schematic?

 

Post what you have so we can all help. Yes, I will give the layout a shot, but you will need to specify every part. It would be best , if you used Eagle for the schematic. That will force force you to pick the parts.

John

 

 

Hi Michael,

I have changed a coupe of minor things as we discussed by PM, added the connection for the pot wiper, and added a decoupling capacitor. I cannot attach these rough drafts to a PM easily (I don't use an off-forum download site). I also kept all the "dots" like you did; although, I would generally use them only when needed.

Note as well that I flipped JP1 to get easier routing. As it is symmetrical, we can redo the connections if you want to see it on the component side. Also, in a final version, I would use copper pours for the V+ and ground, which will reduce considerably the amount of copper you need to remove by etching.

AT THIS POINT CONSIDER BOTH ATTACHMENTS AS DRAFTS

John
View attachment 27484

View attachment 27485

 

Hi Michael,

Here is a revised schematic and board as we discussed. I did not do any copper pours, as that would complicate slightly changes you might want to make. I also exchanged the connections to the servo connector, so it is not on top. Center is still positive. The border size is 2.5 X 1.5" as you wanted. That allows the parts to be spread out a little.

John

View attachment 27491
View attachment 27492

 

Oddly enough i'm getting the exact same issue with this new circuit. The servo just goes to fully clockwise when I connect the battery

 

Can you post a picture of your board, both sides.

John