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Homegrown circuits

I have been quiet for a little while – largely due to a 6 day vacation with the family to Disney. It was a ton of fun, and our kids had a blast – as did Donna and I. We were on the go the entire time, so its not like we really got a chance to unwind and relax, but that’s OK – Donna and I go a little batty when we’ve got extended amounts of downtime. I have also been regrouping on my pump skid control box design andfiguring out some stuff, but none that warranted a blog entry on its own.

Over the past few weeks, I have completely redesigned the control panel and grant PCBs. The control panel was shrunk down in size and re-routed entirely by hand, which has lead to a 1-sided board without any jumper wires. The connector headers also now are completely aligned with the setup of the controls themselves, which will help me keep things straight.

The previous (wireless) grant board design was reworked as a hard-wired single-connection that can be handled by a standard twisted-pair phone wire connection. The power is supplied (and grounded) to this auxiliary board by plugging in the grant, and some on-board capacitors smooth out the power delivery to the LM34, float switches and PICAXE 08M chip. The 08M has just enough inputs and outputs to read these 3 sensors, convert them into a serial transmission, and send them back to the main skid control box via the other twisted pair in the phone cord. I am a little nervous about the current-carrying capacity of the phone lines (typically 24AWG and rated around 0.5A), but that should be significantly more than is drawn by the components – I should be fine.

This long and skinny board should easily fit inside a handle-looking enclosure that (hopefully) spans between the two grant float switches, shown below by the “black box”. I will mount the power LED in the top of the unit so there is a clear indicator that it is working, and put the 3.5mm stereo connector and phone jack on the bottom, which should hopefully provide some protection against moisture exposure (accidental or otherwise). My thought is that it’d be tough to have a random drip hit the underside of the control box in a way that caused a short and fries things. If those connectors have to go on the side due to space limitations or whatever, I’ll have to figure out how to “ruggedize” things for some added protection.

I took some time this weekend to etch the PCBs and solder them up. Initial tests on the grant board indicate performance as expected, much to my suprise and pleasure. I was able to connect to the 08M via the 3.5mm stereo connector and upload the program, and after that the serialized data appeared to be sent out the connector properly. I will use both the control panel and grant PCBs as part of a breadboarded prototype of the main control box internals sometime in the next week or so. That board will be 6″ x 4″ and will represent the biggest and most complex one I’ve done so far, so making sure the design is sound before etching and soldering in components is pretty important.

These were my first real attempts at making printed circuit boards, and I learned quite a bit in the process. The biggest thing was that I can do it successfully… Although I certainly had my share of “educational experiences” along the way:

  • Making cuts to a PCB < 2″ wide with a circular saw will probably end badly, with the board flung across the garage and smashed on the far wall. Best to stick with a jig or band saw.
  • Drilling PCBs takes infinite patience, and quick and controlled movements… even with a drill press. People sneaking up on you while drilling is disasterous.
  • Determine your drill sizes ahead of time (and write them down!!!) with some practice holes on spare PCBs, unless you like going back and re-drilling things.
  • Black toner shows up pretty well on PCBs using the toner transfer method… Green does not (see above picture). Use the “Print in black only” selection in the future.

On another note, some of my hops are rapidly approaching harvest time – I have massive yields on the Nugget and Zeus, and the tips for most appear to be browning a little. Some still have the moist feel to them, but most have that lightly papery feel indicating they need to be picked. The Magnum have been a disappointment this year, although I will probably get something around 1/2oz. I don’t even want to talk about the Cascade or Liberty – I will most likely rip them out next year and plant something else.

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Categories: Hop growing, Tech geeks
  1. August 25, 2008 at 6:16 pm

    Sounds like you’ve been getting all gadgety, shweet.

    At least you’ll be able to harvest your hops, I’m a bad hop bastard. Do you know what style of beer you’re aiming to brew with them? I assume (though I could be wrong) another variety of Homegrown Pale Ale to help show case the hops themselves.

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