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The "Grim Reaper" cometh.

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LAN_403

Conundrum

Sun Sept 10 2017, 05:40AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hi all.

How do you deal with projects that run out of time, money or otherwise turn out to be way more trouble than they are worth.

Its happened to me a few times, notably with the laser PCB etcher but my nearly-working system ended up helping someone else as they bought a ready made module rather than trying to build a driver, and my stepper driver ICs got recycled somewhere.
They also went down the "fail" route, using inadequate parts then switching to better ones when available or affordable.

Someone else has a 3D printer (Mendel IIRC) which never worked right but rather than dumping Â£900+ worth of hardware they kept it.
Probably in some dusty box someplace, which is a shame as the stepper motors were half decent NEMA.

Kind regards, -A

Dr. Slack

Sun Sept 10 2017, 06:15AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

The major project I had that had to be 'dealt with' was back in 1998/2000 when I half built a fighting robot to take part in Robot Wars UK. I ran out of money (my allocation and my employer's support), the team were dissipating, and space in my workshop. I'd got as far as a rolling chassis, but only parts of the 2kJ weapon system had struggled into existence. I needed to reclaim my life, and managed to sell it as a going concern to a builder in Germany, who put a saw on it instead of my complicated weapon, and it got onto German TV, losing in the first round, but at least it fought.

After that experience, I vowed never to have a project on the go that was too large be 'back-burnerised', if there is such a phrase. That is, put into a modest sized cardboard box and pushed under the bench out of sight. It's an interesting test of the quality of my documentation to see how useful it is when I pull it out after a decade. Most of it fails the test and I end up testing, circuit tracing and reverse engineering to find out what the heck I had done. After all, it was so obvious at the time.

A number of my projects are neither success nor failure, but incomplete. I have a signal generator I built perhaps 30 years ago. It has a card rack inside for the extra features that never materialised, so as long as I only want sine or square, and only to 5v pp, it's good.

Sulaiman

Sun Sept 10 2017, 08:31AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

I can not count how many partial projects I have in boxes and biscuit tins

Many are because I wanted to physically build a circuit to check my theory
(I like to design stuff for the sake of it, sometimes I need to get reality checks so physical construction is required)

Many are due to (my) poor design so do not proceed to completion.

Many work to the point that I sattisfy myself that I understand key concepts and it would work if I finished it
- so I get bored don't bother finishing it (yes, I know, I'm weird- OK)

Hazmatt_(The Underdog)

Sun Sept 10 2017, 05:10PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Are you for real? That's like every project I have.

I've been trying to make repairs to this HP 5252 prescaler unit for the HP 5245L counter (nixie tube! YAY nixie tubes!) for 2 years now. I recently narrowed down the problem to the RF board, the time base board is fine. The problem with the RF board is probably a diode went bad, and all of the transistor beta's have drifted to the point of no return. The transistors work, and they show up on the curve tracer, and they do their thing, but their gain is low I know this, these guys are vintage 1963. Some are house marked and I have pretty much given up, I'm not going to bother with the board anymore.

So I'm designing a new prescaler based on the MC12093 x2, which replaces the entire RF binary section of the counter in 2 chips, and so this past Labor day weekend I spent designing the output buffer driver/level shifter to make the MC12093 compatible with the counter input.
Unfortunately I left the bad board still in the counter plugin frame and I wasted 3 days trying to design low power amplifiers that would drive 2-35 MHz into a 30 ohm load! What a headache that was.

When I came home from work Monday night I saw through the open service panel that the board was still installed, removed it and wala! back to 50 ohms! and the simple buffer/driver worked beautifully just the way it should have.

The 3 days lost however, was the time I needed to do the layout for the MC12093, input front end, and inverter transistors for the +13V selector switch to +5V inverted logic to select the division ratio.
At present I have not done any more work on it due to lack of interest (I know it will work now) and I have to find some time to finish it.
Plus I need some time to machine a little RF can for it to go into, but I need the board made first, so this can all wait, it's not a priority.

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