A little electronics hack
Yesterday at the workshop I took out the Laser 128 and circa-1987 Lego electronic parts. They'd been packed away since Maker Faire last year. My new robot barely worked, despite being almost identical to the old robot and running the same software. I found a loose wire connector which Ian fixed. Still had a lot of problems. Neville (a retired EE who first joined the old MARCH group in the mid-2000s and recently came back) started testing things with a meter and scope. He figured out that some of the interface box outputs were only producing half their usual power. We opened the box (a couple of years ago I swapped its plastic rivets for screws). Nothing seemed wrong. It was clean and all of the capacitors looked good for 30+ years old. Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :) We tried the robot again. What a difference! Even before it stopped working last year, the motors always seemed kind of weak. I just assumed that was normal because I never knew it any other way. Now I see what normal is supposed to be. The motors run MUCH stronger! It's an amazing improvement. Neville also resoldered a loose LED connector and one suspect cold joint. So I'm a happy camper. The electronics for this set are running better than ever, which means I can focus on the Lego side and the software. I'm giving a big presentation about all of this Lego stuff on Friday, Nov. 1 at Brickfair NJ and then exhibiting it there Saturday and Sunday. Now I do not have to worry so much about the demo aspect failing.
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up. Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
Yeah just put a penny in the fuse box Sent from: My extremely complicated, hand held electronic device.
On Sep 29, 2019, at 1:55 PM, Mike Loewen via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
It's called a 'crowbar' circuit. Prevents things from burning up.
Thanks. I've heard that term (and seen it used on this list) but never knew what it meant. What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it. On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us> wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
I'm no expert on those circuits. Dave McGuire could probably offers suggestions. Here's some further reading: https://en.wikibooks.org/wiki/Practical_Electronics/Crowbar_circuit On Sun, 29 Sep 2019, Evan Koblentz wrote:
It's called a 'crowbar' circuit. Prevents things from burning up.
Thanks. I've heard that term (and seen it used on this list) but never knew what it meant.
What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us> wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection where it intentionally shorts the output of the power supply. This sounds more like over current protection.
What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it is driving the motors better than it ever has. It may also be your motors are a heavier load than it was intended to drive. If you're interested in investigating further if you point us to schematics we can give suggestions.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us> wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
If you're interested in investigating further if you point us to schematics we can give suggestions.
I am giving the box to Neville in early November (don't want to risk it not working before the Brickfair NJ event the first weekend of that month). He agreed to my request to make a schematic of it. The next step will be to have someone else take his schematic, build one, and send it back to me for testing. That'll prove that the box can in fact be built from just the plans. After that I'll post it on my website. A possible third stage would be to make modern improvements, if any ideas stand out. I'm only interested in the function, not in replicating the physical case. But what I would avoid is replacing the vintage computer with a microcontroller. I'm all for a better interface but strictly against some non-vintage computer experience. On Mon, Sep 30, 2019, 8:43 AM David Gesswein via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection where it intentionally shorts the output of the power supply. This sounds more like over current protection.
What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it is driving the motors better than it ever has. It may also be your motors are a heavier load than it was intended to drive.
If you're interested in investigating further if you point us to schematics we can give suggestions.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us> wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
Looks like someone on this list has already done the legwork on this as of 2016... https://www.glitchwrks.com/2016/09/12/lego-logo-interface On Mon, Sep 30, 2019 at 9:13 AM Evan Koblentz via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
If you're interested in investigating further if you point us to schematics we can give suggestions.
I am giving the box to Neville in early November (don't want to risk it not working before the Brickfair NJ event the first weekend of that month). He agreed to my request to make a schematic of it.
The next step will be to have someone else take his schematic, build one, and send it back to me for testing. That'll prove that the box can in fact be built from just the plans. After that I'll post it on my website.
A possible third stage would be to make modern improvements, if any ideas stand out.
I'm only interested in the function, not in replicating the physical case. But what I would avoid is replacing the vintage computer with a microcontroller. I'm all for a better interface but strictly against some non-vintage computer experience.
On Mon, Sep 30, 2019, 8:43 AM David Gesswein via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection where it intentionally shorts the output of the power supply. This sounds more like over current protection.
What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it is driving the motors better than it ever has. It may also be your motors are a heavier load than it was intended to drive.
If you're interested in investigating further if you point us to schematics we can give suggestions.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us
wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
Looks like someone on this list has already done the legwork on this as of 2016... https://www.glitchwrks.com/2016/09/12/lego-logo-interface <https://www.glitchwrks.com/2016/09/12/lego-logo-interface>
No - that's the card for connecting the computer to the interface box. That schematic already existed and we didn't have the card, so Jonathan (Glitch) built one for us. That is what you see documented. In the current thread I am referring to the interface box itself. There is more info on my personal website at http://www.mindsbeforethestorm.com/8bit_hardware.php. On Mon, Sep 30, 2019, 11:16 AM Mark Whittington <markwhi@gmail.com> wrote:
Looks like someone on this list has already done the legwork on this as of 2016...
https://www.glitchwrks.com/2016/09/12/lego-logo-interface
On Mon, Sep 30, 2019 at 9:13 AM Evan Koblentz via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
If you're interested in investigating further if you point us to schematics we can give suggestions.
I am giving the box to Neville in early November (don't want to risk it not working before the Brickfair NJ event the first weekend of that month). He agreed to my request to make a schematic of it.
The next step will be to have someone else take his schematic, build one, and send it back to me for testing. That'll prove that the box can in fact be built from just the plans. After that I'll post it on my website.
A possible third stage would be to make modern improvements, if any ideas stand out.
I'm only interested in the function, not in replicating the physical case. But what I would avoid is replacing the vintage computer with a microcontroller. I'm all for a better interface but strictly against some non-vintage computer experience.
On Mon, Sep 30, 2019, 8:43 AM David Gesswein via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection where it intentionally shorts the output of the power supply. This sounds more like over current protection.
What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it is driving the motors better than it ever has. It may also be your motors are a heavier load than it was intended to drive.
If you're interested in investigating further if you point us to schematics we can give suggestions.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen < mloewen@cpumagic.scol.pa.us> wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
Mark, that’s the computer interface card. I believe Evan was talking about the controller board (Interface -a) http://4.bp.blogspot.com/-ixfYuILNd9I/U-3meTkPvkI/AAAAAAAAAYI/oqF0-8v-42w/s1... Tony Sent from my iPhone
On Sep 30, 2019, at 11:16 AM, Mark Whittington via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
Looks like someone on this list has already done the legwork on this as of 2016...
https://www.glitchwrks.com/2016/09/12/lego-logo-interface
On Mon, Sep 30, 2019 at 9:13 AM Evan Koblentz via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
If you're interested in investigating further if you point us to schematics we can give suggestions.
I am giving the box to Neville in early November (don't want to risk it not working before the Brickfair NJ event the first weekend of that month). He agreed to my request to make a schematic of it.
The next step will be to have someone else take his schematic, build one, and send it back to me for testing. That'll prove that the box can in fact be built from just the plans. After that I'll post it on my website.
A possible third stage would be to make modern improvements, if any ideas stand out.
I'm only interested in the function, not in replicating the physical case. But what I would avoid is replacing the vintage computer with a microcontroller. I'm all for a better interface but strictly against some non-vintage computer experience.
On Mon, Sep 30, 2019, 8:43 AM David Gesswein via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection where it intentionally shorts the output of the power supply. This sounds more like over current protection.
What are common reasons why those stop working? Neville and I didn't see any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it is driving the motors better than it ever has. It may also be your motors are a heavier load than it was intended to drive.
If you're interested in investigating further if you point us to schematics we can give suggestions.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us
wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry contains a safety mechanism to shut off all power if the current jumps too high, such as a kid inserting a paper clip. There's probably a technical name for that but I do not know it. Anyway, for unknown reasons this circuit was kicking in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning up.
Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
Ah, my mistake. Sorry for the false hope. Best, -Mark On Mon, Sep 30, 2019 at 12:59 PM Tony Bogan <thebogans@mac.com> wrote:
Mark, that’s the computer interface card. I believe Evan was talking about the controller board (Interface -a)
http://4.bp.blogspot.com/-ixfYuILNd9I/U-3meTkPvkI/AAAAAAAAAYI/oqF0-8v-42w/s1...
Tony
Sent from my iPhone
On Sep 30, 2019, at 11:16 AM, Mark Whittington via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Looks like someone on this list has already done the legwork on this as of 2016...
https://www.glitchwrks.com/2016/09/12/lego-logo-interface
On Mon, Sep 30, 2019 at 9:13 AM Evan Koblentz via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
If you're interested in investigating further if you point us to
schematics we can give suggestions.
I am giving the box to Neville in early November (don't want to risk it not
working before the Brickfair NJ event the first weekend of that month). He
agreed to my request to make a schematic of it.
The next step will be to have someone else take his schematic, build one,
and send it back to me for testing. That'll prove that the box can in fact
be built from just the plans. After that I'll post it on my website.
A possible third stage would be to make modern improvements, if any ideas
stand out.
I'm only interested in the function, not in replicating the physical case.
But what I would avoid is replacing the vintage computer with a
microcontroller. I'm all for a better interface but strictly against some
non-vintage computer experience.
On Mon, Sep 30, 2019, 8:43 AM David Gesswein via vcf-midatlantic <
vcf-midatlantic@lists.vcfed.org> wrote:
It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection
where it intentionally shorts the output of the power supply. This sounds
more like over current protection.
What are common reasons why those stop working? Neville and I didn't
see
any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it
is
driving the motors better than it ever has. It may also be your motors
are a heavier load than it was intended to drive.
If you're interested in investigating further if you point us to
schematics
we can give suggestions.
On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen@cpumagic.scol.pa.us
wrote:
On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
Neville noticed something that I wouldn't have. The circuitry
contains a
safety mechanism to shut off all power if the current jumps too
high,
such
as a kid inserting a paper clip. There's probably a technical name
for
that
but I do not know it. Anyway, for unknown reasons this circuit was
kicking
in! He jumped it with an equal-length wire. :)
It's called a 'crowbar' circuit. Prevents things from burning
up.
Mike Loewen mloewen@cpumagic.scol.pa.us
Old Technology
participants (6)
-
David Gesswein -
Evan Koblentz -
Mark Whittington -
Mike Loewen -
Sentrytv -
Tony Bogan