Fishfeeding contraption / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Fishfeeding contraption

1 2 3 next

Move Thread

LAN_403

ragnar

Mon Jul 23 2007, 06:22AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Hi guys,
I took the photos to send them to someone else, but since it does look cute, I think I can get away with posting them here, too.

A friend doing a study of fish learning vs group behaviours asked me to design a contraption that can be used to train his fish. In short, food is dropped into the tank when a coloured light comes on. By using different fish in different tanks, they can be trained to associate the turning on of the light with the dispensing of food.

I played around for a while getting the time constants correct on the chips, and this is what I came up with. When the 'reset' button (to be on the end of that black cord) is pressed, the green and red lights will come on for 60 seconds, and the motor will rotate for 1 second. The circuit will repeat the cycle if the reset button is pressed. (So you can press the button to feed the fish every 12 hours... or something).

Designing the circuit was simple enough. What turned out to be a royal pain in the arse was mucking around with donut-style prototype board to make everything work without too many components on the underside, or too many jumpers where they could short.

Even more of a royal pain in the arse was putting it in a nice grey instrument box in an attempt to make it semiprofessional and even usable.

Perhaps I can start a very vague discussion here...

What is the secret to fast-but-neat prototypes? Does one use a hopelessly oversized box and just hot-melt everything into the lid? Is donutboard ALWAYS this frustrating? How do your prototype 'things' look?

Steve Conner

Mon Jul 23 2007, 08:21AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Hi BP,

That looks very neat. Any time I build a prototype of something, it's usually a horrendous mess. It doesn't matter though because the whole point of prototyping is to get the functioning right. Then you build it again to make it look nice.

1185178896 30 FT28856 2007040318323901 Imgp0883

ShawnLG

Mon Jul 23 2007, 01:57PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

My god you two. You guys need to buy these to prototype with. I use breadboards for most of my prototyping. SMT is a pain for me to prototype with. This is because I would need to make SMT to throught hole converters. If I like what I have built. It will then be finallized on etched PC board.

Steve Conner

Mon Jul 23 2007, 02:13PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Once you've used breadboards for a while, you will probably get sick of them. You can spend hours chasing a problem that's due to a bad contact, a wire that popped out while you were on your coffee break, or just high stray inductance. (That didn't stop Richie Burnett building a 8MHz SSTC on them though.)

The last place I worked in, they were forbidden, and everything was built on stripboard or dead-bugged on bare copperclad PCB.

Also, with many SMT chips, it's not possible to achieve a layout of low enough stray inductance using those through-hole converter thingies. Some won't even work until they are on a 4-layer PCB with a ceramic chip cap at every Vcc/Gnd pair. I have dead-bugged stuff with .025" pin spacing clocked at 125MHz, but beyond a certain point you actually save time and money by just having a PCB fabricated for your prototype. That's why chip makers sell evaluation boards, because the chip is useless on its own until you have a PCB made.

Bjørn

Mon Jul 23 2007, 03:39PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

It does not matter how you do it as long as it is completed in time and works. That usually means knowing what not to do. Like some types of analogue circuits on breadboards.

I use breadboards to verify ideas and when I am sure the ideas will work I make a Conneresque prototype. I don't waste time on schematics, the prototype is the schematic.

The card is a 16 bit I/O card for an Acorn Archimedes RISC computer with a one byte ROM to let the OS know what type of card it is. It took two hours to design and build and worked on the first try.

...

Mon Jul 23 2007, 03:42PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Matt, your problem lies in the fact that you tried to solder the wires under the board. I can't tell from the picture, but I think that is the stuff with 3 connected traces in rows (if it is just plain solder pads it was made for wirewrapping and shouldn't be used for this type of work) which is a start. But you are supposed to run wire on top of the board (I find that solid wire works best, the 30awg silver/kynar wirewrap wire is great once you get used to working with it), cut to length, strip, and solder through the board.

I would give you a few pics of what I am talking about, but most of the finished prototypes I have made were at work, so there is that whole top secret thing...

But I personally prefer to do the prototpye in 2 stages... The first stage is done on a breadboard/etc, and then once you have a design spend a few hours to layout a board and etch it. Also, when you are workin on a breadboard I find it helps a TON to use jumpers that are the exact length (you can get kits that have like .1, .2, .3, ... 2" jumpers or just make them as you go) for at least the power/reset/shtdn/etc lines of the chips, and only have flying wires connecting between distant parts of the circuit.

As to the box, I still haven't found a decent solution besides buying a normal project box and drilling holes in it... For one project I did I used a dicast Al box but replaced the aluminum lid with a sheet of 1/4" stain grade plywood (because I had to a lot of machining on the lid, and I didn't have the proper tools for working with Al), drilling/drinding out the holes, staining, etc. It actually turned out quite nice looking

ragnar

Tue Jul 24 2007, 03:28AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Shawn, I don't use breadboard because stray inductance and stray capacitance turns everything to shit -- and for the same reasons Steve mentioned; bad connections, cooked connectors, lack of permanance.

Yep, Peter, this is the stuff with vertical power and ground strips, and horizontal sets of two pads. It's actually kinda like breadboard, now I think about it. Wiring it from the top is ugly, which is why I avoided that, not to mention there's never enough space to run them around everything -- no excuse. ^_^

Steve, can you post your famous 125MHz dead bug chip? =D

Carbon_Rod

Tue Jul 24 2007, 08:23AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

What is the secret to fast-but-neat prototypes?

1.) Build a working version.
2.) Build a better version and test with client.
3.) Build a production version and test with consumers.
4.) Build the final version.

Step 1 always looks awful:
However, using off-the-shelf servos, aluminum locking channel, and a $4k laptop with fancy graphics always impresses the PHBs....

Sometimes the box is worth more than the contents.... ;P

Steve Conner

Tue Jul 24 2007, 09:01AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I'm sure I've posted this before but meh. It was an 0-40MHz DDS with 125MHz master clock. There are 0805 chip bypass capacitors soldered directly to the IC pins.

CT2

Tue Jul 24 2007, 10:12PM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

I use that board for my tesla coil drivers. I haven't tried etching PCB yet, but the protoboard seems to work fine for what I do. It has the vertical positive and negative rails and then the pads inbetween for your components, I think they cost a few bucks each.

1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob