# Home-etch Controllers



## pshort (May 6, 2008)

Is anyone here into etching PCBs at home? It's pretty easy to do, allows you to make custom controllers, and is fairly inexpensive.

Right now I'm working on the design of a little 0.8" x 1.1" three-channel servo controller. It used a PIC12F510, which has the same pinout as the PICAXE08M that people seem to like to use. As I'm building it (home-etched, PIC12F510, 64Kx8 EEPROM memory chip, voltage reducer) it costs around $2. If I were to use a PICAXE08M the cost would be around $4.

This cost is so low compared with the cost (and physical size) of servos that this may not be worth it for most people. I'm bringing it up just as something that may be of interest to a few. I'll post pictures later today or tomorrow.


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## pshort (May 6, 2008)

Here are the promised photos...

The first shows the etched board (before drilling), the second shows the board after drilling (horrible job of drilling), the third shows the top of the board with everything soldered in place.


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## fritz42_male (May 5, 2009)

That's a neat job - certainly small!

Do you have a schematic?


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## pshort (May 6, 2008)

No schematic yet. It should be easy to generate one, the circuit is pretty simple.


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## pshort (May 6, 2008)

Here's the schematic.

Perhaps I should add a pull-up resistor on the MCLR input.


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## pshort (May 6, 2008)

Still playing with it, mostly aiming at making it (among other things) a recording servo controller. The idea (obviously not original) is to have a recording mode and a playback mode. To use the recording mode a small external potentiometer is attached, and one of the servos moves back and forth as the pot moves and the controller simultaneously records the position of the pot. Switch(es) are used to determine which channel is being recorded. As each servo position is being recorded the other two servos will move back and forth per the previously recorded sequence. 

This project is going on the back-burner for now, as I'm going to be somewhat occupied with other matters. When I pick it up again I'll consider doing a coop buy of the PCB if there appears to be any interest.


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## fritz42_male (May 5, 2009)

Can I also suggest that you look at making it mini-ssc compatible. That would make it soooooo handy!


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## robp790 (Jan 8, 2008)

This idea would be interesting keep us informed.


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## pshort (May 6, 2008)

fritz42_male said:


> Can I also suggest that you look at making it mini-ssc compatible. That would make it soooooo handy!


That's an interesting thought. Since none of the 8-pin PICs have a h/w uart, the serial Rx has to be done in software (firmware). It will be difficult to write it in such a way to keep the servo timing precise and reliably receive data characters, although I think that I may have a way to do it.

And, of course, the board would have to grow (even more) to find a place for the RJ11 connector and the other parts needed for serial reception.

Creeping featurism...where does it end?


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## pshort (May 6, 2008)

OK, I've got the core functionality of the mini-SSC mode firmware running for up to 3 servo outputs. At the moment it's fixed baud rate (9600), servo mode (non-extended) and hard-coded (but changeable) address. This particular version does not make any use of the serial EEPROM. It needs to have the configuration functions added (I consider this to be non-core), and a lot more testing.

It's too close to halloween, and I don't have enough time, to consider any sort of release this year. There are two questions that I need to answer before any sort of release:

1) What would a release consist of? If this was the Christmas forum that I usually visit, I would release the firmware (open-source) and a PCB layout (gerbers), and enough information for other people to be able to run coops and support it. The people who want to use it would then buy bare PCBs from whoever is running the coop, buy the parts from mouser (either directly or through a coop), and assemble the boards. Many of the people in that other forum already have PIC programmers, so they can program their own PICs from the released firmware source files. I'm not sure this work here, since this is a different crowd with only a small amount of overlap with that other forum. Another possibility is that I would sell assembled boards, at some sort of profit. Any comments on this matter? I haven't been around this board long enough to have any real sense of what would work here.

2) What additional features should be added? So far the current firmware doesn't make any use of the serial EEPROM. I'm thinking of adding record/playback functionality. Another possibility is to make it user-programmable similar to a lot of the other controllers out there, although this would a lot more work (by probably an order of magnitude).

3) If it is not programmable, would it be useful to add other non-servo-related functions (such as start/stop or interval timers, random blink LEDs, etc). I'm thinking that there isn't much point in this, since a PICAXE 08M chip could be plugged into the board to accomplish these tasks.


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## fritz42_male (May 5, 2009)

Firstly, thanks for posting this so far - very helpful. You obviously go a lot further with PICs than I do. 

The following comments are from a personal point of view and not intended to put you off - I'm just acting as a Devil's Advocate here (apt in a Halloween forum. lol)

I wouldn't go too far with development as you are then duplicating the features available in the Prop-1 and Prop-2 controller and although there is nothing wrong with healthy competition, I suspect that the sales for both products would be too low for both to eventually survive. Also, if the price approaches the EFX-Tec controllers, I'd be more likely to play safe and buy an existing tested product.

I don't have a PIC programmer and I'm no good at microcode which is why I find the Picaxe range so good.

As it is, I'd definitely buy some existing servo kits off you. I have plans for extensive animatronics for next year and mini-SSC like versions would be very handy. I may get round to doing something on the $10 controller myself re mini-SSC but if you have already done the work then why bother!

I was thinking (& talking to hpropman) about a VERY generic board. ULN2803 option (replaceable by a resistor pack if driving servos), servo input/output style connectors, split voltage so you can drive 12/24V relays and so on. Again, the Prop1/2 series already does this so the price would have to be very low otherwise I wouldn't bother. I'm currently playing with the Kiwi board which has a bit more space on it than the Rev-Ed project boards and are just as cheap.

I suppose (rambling mode off) what I was thinking of was of maybe having 2 or 3 custom fabricated boards available as kits in a group buy each of which would accomplish specific tasks. I prefer to have multiple independant boards as it makes life a lot easier to fault find. Ideally the boards would have optional 5V regulators but also be capable of being battery pack driven. One or 2 would be a mini-SSC controller with 3 or more servo outputs (08M and 14M or PIC equivalents), a relay timer, a random blink multipl LED driver (preferably with optional fading up and down LEDs - mine just currently blinks on and fades off via a decent electrolytic across the LEDs). That's about it.

Just another point, I'm now playing with the 20X2 chip - this is pin compatible with the 08M and 14M chips but runs a lot faster and has a lot more memory as well as other features. Price is still low though. A 'really' generic board would allow any of these 3 variants to be plugged in.

I'm already on a co-op buy for SSR boards on DIYXMAS forum and although I have yet to take delivery, this seems like a good way to go.

Hope these comments are useful and thanks again Phil.


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## pshort (May 6, 2008)

Just brainstorming, so don't take what I say as arguing...

If it was just a functional equivalent at a slightly lower price, there would be no point in trying to 'market' it. However...

1) It is physically a lot smaller than the Prop-1, Prop-2, etc controllers. If it was suitable potted or conformal coated it might make a lot of sense to put the servo controller inside of the prop in situations where those other controllers are too large, cuts back on the wiring and makes it easier to conceal it (the wiring).

2) It's a lot lower cost...the Prop-1 is $40, the Prop-2 and SX are $100. Although I'm not sure if this matters, given the typical cost of servos and props in general. I'm not going to put a price on it now, since I haven't decided if I'm going to try and make a living at this sort of thing or not, but those Prop-X products appear to be pretty high margin to me.

3) It is inexpensive AND could have a record-playback mode. This would be useful for standalone props.


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## fritz42_male (May 5, 2009)

1) - This is fine although I would prefer it not to be potted/coated as I might want to change bits myself (recent example is a Cowlacious board where Carl put a different resistor in for me so I could trigger the sound board off 240V rather than the 120V the board was designed for). However, size is important (lol) and smaller is better as far as props are concerned. I love the servo style output/input format connector but on my next $10 boards I'll be using sockets for the 330 ohm resistors so I can bypass them when I need to trigger SSRs etc.

2) - I don't know if you have ever had your own business but trust me when I say that you need to be looking at at least 50% - 100% markup . If you are selling kits then labour is a much smaller element. Have you looked at Cowlacious's site? He offers kits and assembled units and for the price he charges for assembled, I really can't believe he even covers his labour costs.

3) - This is an excellent feature. If you can build in joystick movement monitoring and then use the same connectors for playback then this would be a winner. I can't see any problem with this as the 330 ohm fixed offset for the servo connector can be dealt with in software when plugging in pots for the recording function. Being able to record to PC AND to serial EEPROM would be neat. This would mean you could test and refine recorded movement with VSA then transfer to a stand-alone controller.

4) - liability. I can't understate the importance of considering liability. The world is becoming increasingly litigacious. If you have to consider this aspect of business then this will throw your whole business model out of the window. If you could speak to one of the other small vendors (don't know how they would react to talking to a potential competitor) and find out how they deal with it then this would be a good thing to do.

5) - Why not do it from a hobbyist point of view first - this would allow you to gauge demand (fairly limited for Halloween stuff) and make a bit of useful money on the side. The profits might help you pay for your hobby. You can do a lot in leisure time.

6) - Make your stuff as generic as possible. I've designed up a little 08M/14M board that is as adaptable as possible but stalled the project for the moment - I was considering redesigning for the 20X2 to be included as well. As well as the small specific boards, a good overall board would cover the three PIC variants of the 08M/14M/20X2 - all pinout compatible. Have a socket for the serial EEPROM for optional use and so on. One idea from hpropman was to come up with vertically orientated 'daughter' boards - possibly FETS for DC SSR, Triacs for AC SSRs, zero crossover functioning for AC SSR circuits so you can use PWM dimming and so on. Make it easy to do fault finding - in my case, I use LEDS for checking almost everything. I can use them for testing on/off for relays, PWM and servo outputs and so on. Also useful when checking inputs if you can build the option into design. 

If you go down the daughter board route maybe have a liitle line-input board so we can have a sound to servo function built in.

7) - support. This is critical. You can spend a lot of costly time on support. Have a good FAQ and a chargeable service for checking/repairing boards. The more downloadable routines you have for your products, the more you will sell. I've borrowed code from hpropman (thanks Joe), the Picaxe forums etc etc. Anciliary stuff such as how to make animatronics WITH dimensions & component/cuting lists would be so handy. I've recently bought $40+ worth of 2 "howto's" (waiting for one of them to arrive) and although the other one is a good guide, I'd love to have had printable PDF plans that I could have overlaid onto ply or whatever to build EXACTLY what was suggested. Then offer professional versions of the kits. A perfect example is that I want to build 2 axis eyes - kits exist but they are quite expensive particularly when I look at what people want to charge for postage to Oz ($56 in one case for a small packet!). Ply can replace lexan/perspex and so on for hackers like myself.

8) - socket as much as possible if you are offering stuff in kit form. I've messed up a few boards in my time and being able to transfer the expensive bits to new boards was very handy.

9) - Look for the widest appeal possible. The Halloween side of things is limited - Xmas is obviously another option. An adaptable kit could handle servo and trigger control for Halloween and if the same kit could be used for lighting sequences for Xmas then perfect!


Hope this is of help.

Cheers

Mike


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## fritz42_male (May 5, 2009)

Oh and building in SPI code and a connector would be darned handy. 

The other thing is sound record/replay. The ISD chipcorder chips are reasonably priced but need setting up and a reasonable amount of support components. I recently picked up a USB bus 50 second board from electronics123 that works really well but not sure what chipset it uses (epoxy covered job). Support for a cheap and easy to use solution like this would be brilliant (via a daughter board). Again, stackable might be the way to go. Common power etc.

Now, that's you sorted for the next 6 months - anyone else? lol


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## pshort (May 6, 2008)

Thanks.

The overhead for organizing a corporation or LLC is quite high, and one would have to sell a lot of cheap gadgets to cover those fixed expenses. It probably doesn't pencil out, so the project may stay in the lab for a long time...


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## pshort (May 6, 2008)

Incidently, I just noticed the 300 Ohm series resistors that you are incorporating on the control signal wire. What are they there for? I've noticed that a lot of controller circuits do not seem to include them.


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## fritz42_male (May 5, 2009)

Dunno actually. All the Picaxe servo driver circuits showed them so I figured they were part of the spec! I know it gave me a problem getting my SSRs to fire though. lol

PLEASE don't let my comments put you off totally. If you organize this as a hobby, you could make useful money from limited outlay and just duplicating work you would probably do for your own benefit. I'm not saying it will pay you big bucks but if you are considering getting some production boards done for yourself, then selling the spares would probably pay for your own stuff plus a little extra.

All you need is a PayPal account to receive payments and you are sorted. I'd place an order for 3 or 4 mini-SSC controllers now!


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## pshort (May 6, 2008)

Not to worry. I've gone through a similar process before over at doityourselfchristmas.com (and preceding sites) with the Renard design. The Renard dimming controllers (basic scheme, all the firmware, and the Ren64 board design itself) were all my doing (on a non-profit, pay-it-forward basis). Other people stepped in with additional board designs and a huge amount of support, and it was very rewarding to me, but it still took a lot of effort on my part. This memory, plus a lesser familiarity with this community, is the basis of any hesitancy on my part.

In any case I'll probably have more time available later this year and early next year, so this story may change. One thing that I'd like to do in addition is to get some more servo-related plugins written for Vixen, perhaps starting with a mini-scc plugin.


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## fritz42_male (May 5, 2009)

You are the creator of Renard?


We are not worthy!


Seriously, that's a very nice bit of work. NOW I'm starting to believe that it might be worth your while going into business.


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## pshort (May 6, 2008)

Today I etched and assembled the next rev of the board, and received a bunch of micro-servos in the mail. Now to figure out what to do with them for testing the board...


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## fritz42_male (May 5, 2009)

Where do you get your micro servos? I get mine from dealextreme.

So you don't bother with the 330 ohm resistors for the servo control line? If I take them out of my design that will simplify my board greatly.

Microservos as eyebrow control?

Christian pigdog - I keeel yewww!


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## pshort (May 6, 2008)

From hobbyking.com. These are the first servos that I've purchased, apart from one that I bought from a local hobby store.

As for the 300 ohm resistors, I'll look into it more.

I'm pretty much a neophyte with all of this servo stuff, so don't take anything seriously that I say or do in this area. I'm still got a lot of learning ahead of me...


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## fritz42_male (May 5, 2009)

pshort said:


> From hobbyking.com. These are the first servos that I've purchased, apart from one that I bought from a local hobby store.
> 
> As for the 300 ohm resistors, I'll look into it more.
> 
> I'm pretty much a neophyte with all of this servo stuff, so don't take anything seriously that I say or do in this area. I'm still got a lot of learning ahead of me...


Wow - they sure are cheap!


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## hpropman (Jul 27, 2008)

The 330ohm resistors are to protect the input port in the chip (according to Rev Ed anyway) I have always included them. If you have trouble with the SSR's then I would try a smaller resistor or eliminate completely. Remember that the picaxe primary market is for education so they are prob just being cautious with there documentation.


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## fritz42_male (May 5, 2009)

Thanks Joe. Got the same answer off the picaxe site - I'll try lower values of resistor until I can get the SSR to fire reliably and then test with servos as well.


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## pshort (May 6, 2008)

For now I'm running a blog about this...don't know how long I'll keep it going, though.

http://diyservocontroller.blogspot.com


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## fritz42_male (May 5, 2009)

Nice solution to the voltage supply issue. The 8 pin pics have very low consuption levels so perfect!


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