Analog servo tester (with cycle)?

[Andy W]

Has anyone seen a circuit to cycle a servo continuously?
I know I can make a servo move with a simple 555 circuit, but can I get it to cycle between two adjustable endpoints for an extended period? I'm thinking a "warbling" or "police siren" style circuit (slowed down) with a dual timer?
..a

[Comatose]

Andy,

Its not analog, but I have a whole bag of circuits that can do that spare. I designed them for a class I TAed, and after a semester of use we decided to redo them to make them more freshman-proof (reverse polarity protection, larger potentiometers, that sort of thing)

The circuit has two identical outputs and three trim pots. Two of the trim pots set endpoints and the third sets rotation speed. Takes seven to twelve volts as an input.

I can send you one free if you want it, as they're obsolete surplus.

[Andy W]

Cool.. I'll PM you..
Thanks,
..a

[Comatose]

Andy, I mailed the cycler today.

Basic functionality is as follows: the switch starts and stops rotation. The center position is stopped and either up or down is moving.

The trim pot nearest the switch is speed. It goes from approximately 100 ms per cycle to about 10 seconds.

The other two pots are the endpoints. You can change the extent and the position of the sweep (i.e 10 degree sweep between 0 and 10 degrees or between 30 and 70 degrees or whatever)

[rc-eflyer]

Comatose,

You wouldn't happento have any more of those babies laying
around by chance :rolleyes: . Be glad to pay shipping if not too
much :) .

Thanks,
Steve

[Andy W]

Thanks again - I can't wait to try it. I have some 'suspect' servos I plan to put through some exercise before I put them in a model.
..a

[Comatose]

Oh, the other thing I should mention. The signal wire of the servo goes towards the edge of the board. Both outputs are the same.

rc-eflyer, I have more of the boards. The only issue is we're reusing the PICs , so for Andy's I just used one from my free sample stash (thanks Microchip). If I send out too many I'll burn through my stash of extra PICs. I can send you one for the cost of a PIC ($1.33) plus the cost of mailing it ($1.12) plus the cost of a padded envelope ($.40), so call it an even three bucks.

I'd also like to make sure Andy's makes it through the mail undamaged before sending more of them out.

I have approximately ten of the ones that were reworked midsemester to make them a bit more impervious to damage.

[rc-eflyer]

Oh, the other thing I should mention. The signal wire of the servo goes towards the edge of the board. Both outputs are the same.

rc-eflyer, I have more of the boards. The only issue is we're reusing the PICs , so for Andy's I just used one from my free sample stash (thanks Microchip). If I send out too many I'll burn through my stash of extra PICs. I can send you one for the cost of a PIC ($1.33) plus the cost of mailing it ($1.12) plus the cost of a padded envelope ($.40), so call it an even three bucks.

I'd also like to make sure Andy's makes it through the mail undamaged before sending more of them out.

I have approximately ten of the ones that were reworked midsemester to make them a bit more impervious to damage.

Sounds fine to me :D . Let me know how you want the money and thanks
again.

Steve

[Andy W]

I'll look out for it and post here..
..a

[Chippie]

[QUOTE=Comatose]

rc-eflyer, I have more of the boards. The only issue is we're reusing the PICs , so for Andy's I just used one from my free sample stash (thanks Microchip). If I send out too many I'll burn through my stash of extra PICs.

QUOTE]

Comatose, how about releasing the hex code for the chip if it aint copyright..might help a few people who can burn but not write asm. like me lol...... :D

ooops.... a circuit might help too..... :p

[Hovertime]

http://www.rc-cam.com
Mr. RC-Cam has this DIY project , look under special projects, project named RCST.
Has hex file schematics and parts list...
This little gizmo does it all:)

[Andy W]

I was orginally looking for an analog design, but was saved from a few nights of breadboard word by the kind gentleman above.. :)
..a

[Dan Baldwin]

A.
It should be easy to do it analog fashion with 2 555s or a 556. Want a circuit, or are you taken care of?

Dan

[Andy W]

I wouldn't mind a circuit anyway..
..a

[Dan Baldwin]

Andy
I haven't breadboarded this (I don't have any 555s with me) so the component values are basically guaranteed to be wrong, and it's possible that a mistake or two has snuck in. If I get a chance, I throw it on a board tomorrow.

Dan

EDIT
new schematic

[Hovertime]

I think that RC-man digital project is by far less complicated, only trouble if you don't have pic programmer.
But since you are getting one already made, it does not matter;)

[Andy W]

I've seen digital projects, I just wanted an analog one as I have all the pieces.
As you say, I don't have to worry about it now.. :)
..a

[Comatose]

For the people who are asking for hex files and circuit diagrams and whatnot, I can post them, but that's kinda missing the point. This circuit wasn't designed to be a servo tester. I TAed a class called Stress Analysis, which had as a major portion of the class a design project where the students made lifting mechanisms. The winner was the one who lifted the 12 ounce weight the greatest height/the weight of their mechanism. The weight was mounted on a linear bearing to a pole about three feet away, and there was an obstacle between the designated mounting point and the pole which they had to go over or around. I convinced the professor to use servos for the lifting mechanism, as they're easy to use, relatively cheap and most importantly uniform. So, I had to cook up and assemble servo controllers for that class. They're really designed for that. They have a switch for flipping the servo from one preset endpoint to the other, two potentiometers to set those endpoints and one that sets speed. It just so happened that in another class I was taking we needed to have a servo oscillating continuously as a lane selector for one of those rube goldberg looking gumball machines with tracks and lifts and loops and that sort of thing. Having the boards, I just wrote some modified software for continuous oscillation. Now, by the end of the semester, (the class had never had a design project before, we were tyring something new) it had become apparent that while the project on the whole was a great success, the durability of the servo controllers was somewhat lacking. The main problems were the following: The input had no protection against reverse voltages. The controller was given to the students as a bare board, so the bottom was easy to short out (the structures were made of aluminum , so the lab had conductors everywhere.) The battery snap (9v battery connectors were used) was extremely easy to break. Worse, when they broke it sometimes resulted in a short inside the snap. finally, we had used trim potentiometers for all the adjustments. These were somewhat cumbersome to use and several enthusiastic teams had broken one or more by trying to set the endpoints to beyond the stops with a big screwdriver. None of those problems were really the fault of the board, I'd just designed them to be used with somewhat more care than they were shown. So we decided to remake the boards to be more user friendly and much more impervious to rough handling. As a result, I have a large number of board which, although they aren't primarily designed to perform the task, make fairly nice servo testers. I also have code that makes them rotate continuously. We pulled the microcontrollers from the old boards to go into the new ones, so the old boards are basically just taking up space for me. I didn't have the heart to throw them out.

Given that rather lengthy explanation, when Andy posted looking for a servo tester, I had one to give him. The same for the few other people who have contacted me about getting one: I'm able to hand them out because they were already paid for, I was paid (TA wages) to make them and they were already used for their designed purpose. They're now obsolete and largely valueless (the components on them new were worth about $3). They are okay servo testers, but they're not exactly optimal for that purpose.
Case in point: they have voltage regulators built in, and the servo runs draws its drive power from the regulator. This is entirely unnecessary and inefficient for a servo tester. They're that way because, for the purposes of our competition, we wanted to remove the "my battery wasn't completely charged" or "I used super-premium batteries with higher voltage under load" type irregularities. I have them, and you're welcome to them. I'm even offering to provide and program new PICs for them for cost (the pics that they used to have are now in the new revision and belong to CMU), but it seems silly for someone to perfboard up the circuit and burn their own pic for them, because they're less than optimal for being a hobby servo tester. I could certainly design and write code for a purpose-built pic12f675 servo tester, but chances are it'd look a lot like the one on Mr. RC-cam's site.

That being said, if anyone still wants the schematic or hex file, I'll post them.

[Dan Baldwin]

I breadboarded the 'ciser this morning, and it worked like a charm. It's out there working over an HS-81 right now. The component values were actually very close. The only change that needs to be made is the 15 K resistor that goes between the diode and the pot in the output line from the right hand 555 needs to be made much smaller. 3.3k seems to work well. I'll attempt to edit the post that contains the schematic to show the proper value.

Dan

[Andy W]

I'd also like to make sure Andy's makes it through the mail undamaged before sending more of them out.

Got mine yesterday - hadn't been to the post office in a few days - and it's in good shape - 7805 was bent against board, but I expect that was needed to get it in the envelope anyway.
Haven't hooked it up yet - I'll report back when I do.
THANK YOU!!
..a

[rhenningsen]

Comatose:
I want to be able to drive a sevo from one end to the other so I can actuate one of my old servos to trip a camera using a relay contact? The relay could either energize the circuit or set the potentiometer values.
I want to attach the servo to a camera in order to trip the shutter with an Infra red sensor.
This will detect a "warm-body" presence and take a snaphot.
thanks in advance for your expertise.

Looking at your schematic: do the three connections (ground, servo, 5v) go to the black,signal,red on a servo connection?

If you can help me with the connections to the servo, I'd really appreciate a servo controller board
Let me know

[Comatose]

The schematic posted here isn't for my servo controller, mine's microcontroller based. The discussion here was for a servo tester that cycled continuously. That being said, mine with its original program could do that without too much trouble.

I can send you one for $3 programmed and shipped (covers the cost of shipping and a new pic.) To trigger it with a relay, what you'd do is leave the switch in the center position, and solder wires to the center and either the front or the back pad of the switch. Run those wires to your relay. An open circuit between those pins will send the servo to one (adjustable via a trim pot) endpoint, and a short will send it to the other.

[rhenningsen]

QUOTE=Comatose]The schematic posted here isn't for my servo controller, mine's microcontroller based. The discussion here was for a servo tester that cycled continuously. That being said, mine with its original program could do that without too much trouble.

I can send you one for $3 programmed and shipped (covers the cost of shipping and a new pic.) To trigger it with a relay, what you'd do is leave the switch in the center position, and solder wires to the center and either the front or the back pad of the switch. Run those wires to your relay. An open circuit between those pins will send the servo to one (adjustable via a trim pot) endpoint, and a short will send it to the other.[/QUOTE]


Yes please! How about I send you $10 and you provide me with a sketch/diagram that shows me what to do? I think that I understand what to do, but it's not crystal clear.
Also explain how to set up total end-to-end travel points
If you have one mounted on a circuit board etc, I can pay more
What is the best way to pay. I have Pay-Pal
Thanks!

[Comatose]

Here, I attached a picture of what I have. As originally designed, the switch toggled the servo from one endpoint to the other as set by the potentiometers. To interface to something else, the easy way would be to keep the switch in the center (off) position and solder the signal you want to feed to the center pad of the switch. There's a 1k ohm pull-up resistor on that line, so if you want to trip it with a relay, all that would be required is soldering two wires onto the ground and signal pads of the circuit and then having your relay close a connection between them, or I'd be happy to desolder the switch and add those wires for you.

Paypal works for me. jjb2 (AT) andrew.cmu.edu with the proper @ symbol.

How much of your detector circuit do you have done/designed? If you're done up to the relay, then with this you're two solder joints away from done. You set total travel by setting the endpoints, they range from full clockwise to full counter-clockwise, so travel can be anything in between. You reverse the rotation direction the same way.

[rhenningsen]

Comatose,
Money is on it's way via Paypal
thanks
bob

[Comatose]

Robert,

Servo controller is on itsway, I'd guesstimate that it'll get there either saturday or monday. However long it takes first class mail to ge between ohio and NV.

I soldered a pair of wires onto the circuit, so when it gets to you test it as follows: first, plug a servo into either of the servo connector headers. The signal wire goes towards the edge of the board. if you keep the white wires separate, flipping the switch either up or down will trip the rotation. Up and down are the same, center is the other position. Next, put the switch in the center position and cros the ends of the white wires. Crossing and uncrossing the wires should also trip the servo.

If that all works, attaching the wires to the contact terminals of a relay should make the servo tripped by the relay. Adjust the rotation speed and endpoints you want, and you should be good to go.