Crowbars...

On Mon, 24 Jul 2023 09:22:50 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmowery42@charter.net> wrote:

In article <dp4qbi5nihq1fokl0fb2jun9n4e3s0a5kr@4ax.com>,
jlarkin@highlandSNIPMEtechnology.com says...

A giant SCR crowbar would be easy. A zener and an SCR. And a fuse
maybe.




I vote for that all so for a quick fix. Simple and no adjustment.

Soft triggering an SCR, from a zener, is a potential failure mode, but
the SCR would fail shorted, which is better than blowing out the RF
stuff.

Well, by a strange coincidence I only recently bought a load of diacs
which breakover at 32V. I could pick the lowest breakover device out
of the bunch and maybe shave a volt or so off of that and that sorts
out the soft-trigger problem as well.
Click to expand...

That\'s perfct if you can tolerate 32v. Get an SCR with an inherent
gate-cathode resistor, or just add one so the diac sees the full rail
voltage before it fires.

Diacs are wonderful gadgets. I\'ve tried to replicate the diac function
with discretes and it ain\'t easy.

An RC-Diac-LED or better yet DepletionFet-Diac-LED can make a bright
warning flasher on a high-voltage power supply that draws very little
current.
 
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
Click to expand...

<snip>

> By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.

People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage.

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf

Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink, and how fast the current sink has to turn on, which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.

--
Bill Sloman, Sydney
 
On Monday, July 24, 2023 at 7:55:38 AM UTC-7, Anthony William Sloman wrote:
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
snip
By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage..

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf
Click to expand...

I know i can sink more current with another FET or something. But if one part fail, that 50% chance of failing. However, i can put 10 sets of zeners with each sinking 1A. One failure is only 10%. 10 zeners aren\'t much more expensive than a FET.

> Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink,

Actually, around 3A to 5A for a 3KWhr batteries.

> and how fast the current sink has to turn on,

12V zener turns on at 80% SOC. It doesn\'t need to be fast. It can be overnight. I seldom charge it to 90% anyway. Even if I have to, it\'s OK to lose some energy to heat slowly.

> which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.

I am adding new portable batteries (2 to 3KWhr). It\'s roughly 2A per KWhr MAX.

I have told the audience many times, but not everybody, everywhere and all at once.
 
On Monday, July 24, 2023 at 8:14:22 AM UTC-7, Eddy Lee wrote:
On Monday, July 24, 2023 at 7:55:38 AM UTC-7, Anthony William Sloman wrote:
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
snip
By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage.

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf
I know i can sink more current with another FET or something. But if one part fail, that 50% chance of failing. However, i can put 10 sets of zeners with each sinking 1A. One failure is only 10%. 10 zeners aren\'t much more expensive than a FET.
Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink,
Actually, around 3A to 5A for a 3KWhr batteries.
and how fast the current sink has to turn on,
12V zener turns on at 80% SOC. It doesn\'t need to be fast. It can be overnight. I seldom charge it to 90% anyway. Even if I have to, it\'s OK to lose some energy to heat slowly.
which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.
I am adding new portable batteries (2 to 3KWhr). It\'s roughly 2A per KWhr MAX.

I have told the audience many times, but not everybody, everywhere and all at once.
Click to expand...

PS:

By the way, the 384V batteries are composed of 32x 12V modules in 16 groups of 24V. They are charged at 168V (7x) and discharge at 384V (16x).

For energy shifting, I am using a servo motor driving a 16P2T rotary switch.. I can use bi-directional switching between 192V and 24V, but I would need positional sensing on the switch. If I just use uni-directional switching, there will be three positions: 192V, +24V and -24V.

O O O O O O
=== === 192V
=== === +24V
=== === -24V

There is another set of switch/relay to double it to 384V.
 
On Monday, July 24, 2023 at 8:36:02 AM UTC-7, Eddy Lee wrote:
On Monday, July 24, 2023 at 8:14:22 AM UTC-7, Eddy Lee wrote:
On Monday, July 24, 2023 at 7:55:38 AM UTC-7, Anthony William Sloman wrote:
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
snip
By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage.

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf
I know i can sink more current with another FET or something. But if one part fail, that 50% chance of failing. However, i can put 10 sets of zeners with each sinking 1A. One failure is only 10%. 10 zeners aren\'t much more expensive than a FET.
Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink,
Actually, around 3A to 5A for a 3KWhr batteries.
and how fast the current sink has to turn on,
12V zener turns on at 80% SOC. It doesn\'t need to be fast. It can be overnight. I seldom charge it to 90% anyway. Even if I have to, it\'s OK to lose some energy to heat slowly.
which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.
I am adding new portable batteries (2 to 3KWhr). It\'s roughly 2A per KWhr MAX.

I have told the audience many times, but not everybody, everywhere and all at once.
PS:

By the way, the 384V batteries are composed of 32x 12V modules in 16 groups of 24V. They are charged at 168V (7x) and discharge at 384V (16x).

For energy shifting, I am using a servo motor driving a 16P2T rotary switch. I can use bi-directional switching between 192V and 24V, but I would need positional sensing on the switch. If I just use uni-directional switching, there will be three positions: 192V, +24V and -24V.

Remove the \'.\':
O.O.O..O.O.O
===......===..........192V
.....===.....===..... +24V
.......===......===... -24V

There is another set of switch/relay to double it to 384V.
Click to expand...
 
On Tuesday, July 25, 2023 at 1:14:22 AM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 7:55:38 AM UTC-7, Anthony William Sloman wrote:
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
snip
By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage.

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf

I know i can sink more current with another FET or something. But if one part fail, that 50% chance of failing. However, i can put 10 sets of zeners with each sinking 1A. One failure is only 10%. 10 zeners aren\'t much more expensive than a FET.
Click to expand...

If you design the current dump carefully, it is very unlikely to fail. The stuff I put into production only failed if the semiconductor manufacturer sold us parts that didn\'t meet their specs. The only example I can remember was a single Hewlett-Parkard opto-isolator that was much slower than it should have been - when the service engineer found out which part was creating the problem he just replaced it. It was very unexpected and the manager got one of the other engineers to check my worst case propagation numbers, which were fine. Many years earlier I\'d run into a TI digital latch which was fine at room temperature but got too slow when you closed the cabinet and the ambient got warmer. We found that with a hot air gun and a part swap cured the problem - but that was on a development machine and management didn\'t get into the act.

Adding redundancy is rarely cost-effective or sensible.,

Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink,

Actually, around 3A to 5A for a 3KWhr batteries.
Click to expand...

So 37.5 to 62.5 W which is quite a bit. Turning off the charger would be cheaper and easier.

and how fast the current sink has to turn on,

12V zener turns on at 80% SOC. It doesn\'t need to be fast. It can be overnight. I seldom charge it to 90% anyway. Even if I have to, it\'s OK to lose some energy to heat slowly.
Click to expand...

But dissipating that heat costs money. Heat sinks aren\'t free and neither is the ventilated space they need to do their job.

which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.

I am adding new portable batteries (2 to 3KWhr). It\'s roughly 2A per KWhr MAX.
Click to expand...

Which neither detailed nor helpful.

> I have told the audience many times, but not everybody, everywhere and all at once.

And you haven\'t told us anything like enough. Dumb newbies never do.

--
Bill Sloman, Sydney
 
On Monday, July 24, 2023 at 8:52:26 AM UTC-7, Anthony William Sloman wrote:
On Tuesday, July 25, 2023 at 1:14:22 AM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 7:55:38 AM UTC-7, Anthony William Sloman wrote:
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
snip
By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage.

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf

I know i can sink more current with another FET or something. But if one part fail, that 50% chance of failing. However, i can put 10 sets of zeners with each sinking 1A. One failure is only 10%. 10 zeners aren\'t much more expensive than a FET.
If you design the current dump carefully, it is very unlikely to fail. The stuff I put into production only failed if the semiconductor manufacturer sold us parts that didn\'t meet their specs. The only example I can remember was a single Hewlett-Parkard opto-isolator that was much slower than it should have been - when the service engineer found out which part was creating the problem he just replaced it. It was very unexpected and the manager got one of the other engineers to check my worst case propagation numbers, which were fine. Many years earlier I\'d run into a TI digital latch which was fine at room temperature but got too slow when you closed the cabinet and the ambient got warmer. We found that with a hot air gun and a part swap cured the problem - but that was on a development machine and management didn\'t get into the act.

Adding redundancy is rarely cost-effective or sensible.,
Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink,

Actually, around 3A to 5A for a 3KWhr batteries.
So 37.5 to 62.5 W which is quite a bit. Turning off the charger would be cheaper and easier.
Click to expand...

3A to 5A MAX when the batteries are empty. Less than 1A at 80%. mA\'s at 90%.

and how fast the current sink has to turn on,

12V zener turns on at 80% SOC. It doesn\'t need to be fast. It can be overnight. I seldom charge it to 90% anyway. Even if I have to, it\'s OK to lose some energy to heat slowly.
But dissipating that heat costs money. Heat sinks aren\'t free and neither is the ventilated space they need to do their job.
Click to expand...

They are warm to be touched. No heat sink necessary.

which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.

I am adding new portable batteries (2 to 3KWhr). It\'s roughly 2A per KWhr MAX.
Which neither detailed nor helpful.
Click to expand...

The motor draws around 20A to 30A peak out of 24KWhr battery. So, just a couple of A\'s from each portable. Perhaps a bit more when fast charging an empty one. But so far, the 3A fuses are holding up. The rotary switch is capable of 3A and the wires are at least 5A.

I have told the audience many times, but not everybody, everywhere and all at once.
And you haven\'t told us anything like enough. Dumb newbies never do.
Click to expand...

Dumb readers don\'t read everything either.
 
On Monday, July 24, 2023 at 8:41:10 AM UTC-7, Eddy Lee wrote:
On Monday, July 24, 2023 at 8:36:02 AM UTC-7, Eddy Lee wrote:
On Monday, July 24, 2023 at 8:14:22 AM UTC-7, Eddy Lee wrote:
On Monday, July 24, 2023 at 7:55:38 AM UTC-7, Anthony William Sloman wrote:
On Monday, July 24, 2023 at 11:49:33 PM UTC+10, Eddy Lee wrote:
On Monday, July 24, 2023 at 1:23:00 AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:
In article <dp4qbi5nihq1fokl0...@4ax.com>,>jla...@highlandSNIPMEtechnology.com says...
snip
By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
People who can design electronic circuits know how to set up an circuit that will start drawing current when the voltage at its input hits 12.5V or any other arbitrary voltage much over about 2V. (1.2V is about the lowest voltage reference you can buy easily) and its a matter of comparing a divided down version of the input voltage with your chosen reference voltage, and turning on a current sink when the input is higher than you chosen voltage.

The LM10 does offer a 200mV reference voltage output, but it isn\'t cheap.

https://www.ti.com/lit/ds/symlink/lm10.pdf
I know i can sink more current with another FET or something. But if one part fail, that 50% chance of failing. However, i can put 10 sets of zeners with each sinking 1A. One failure is only 10%. 10 zeners aren\'t much more expensive than a FET.
Actually working up the circuit isn\'t worth the effort until you know how which much current you need to sink,
Actually, around 3A to 5A for a 3KWhr batteries.
and how fast the current sink has to turn on,
12V zener turns on at 80% SOC. It doesn\'t need to be fast. It can be overnight. I seldom charge it to 90% anyway. Even if I have to, it\'s OK to lose some energy to heat slowly.
which usually means telling the audience what you are actually trying to do. Keeping a Nissan Leaf running after it batteries have hit the end of their service life isn\'t detailed enough to be helpful.
I am adding new portable batteries (2 to 3KWhr). It\'s roughly 2A per KWhr MAX.

I have told the audience many times, but not everybody, everywhere and all at once.
PS:

By the way, the 384V batteries are composed of 32x 12V modules in 16 groups of 24V. They are charged at 168V (7x) and discharge at 384V (16x).

For energy shifting, I am using a servo motor driving a 16P2T rotary switch. I can use bi-directional switching between 192V and 24V, but I would need positional sensing on the switch. If I just use uni-directional switching, there will be three positions: 192V, +24V and -24V.

Remove the \'.\':
O.O.O..O.O.O
===......===..........192V
.....===.....===..... +24V
.......===......===... -24V

There is another set of switch/relay to double it to 384V.
Click to expand...

PPS:
I guess I still need position sensor to make sure it stop at position #1 for 168V and 192V.
No energy need to keep in position. Namely, bi-stable or tr-stable relays.
 
On Mon, 24 Jul 2023 06:49:28 -0700 (PDT), Eddy Lee
<eddy711lee@gmail.com> wrote:

On Monday, July 24, 2023 at 1:23:00?AM UTC-7, Cursitor Doom wrote:
On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin
jla...@highlandSNIPMEtechnology.com> wrote:

On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmow...@charter.net> wrote:

In article <dp4qbi5nihq1fokl0...@4ax.com>,
jla...@highlandSNIPMEtechnology.com says...

A giant SCR crowbar would be easy. A zener and an SCR. And a fuse
maybe.




I vote for that all so for a quick fix. Simple and no adjustment.

Soft triggering an SCR, from a zener, is a potential failure mode, but
the SCR would fail shorted, which is better than blowing out the RF
stuff.
Well, by a strange coincidence I only recently bought a load of diacs
which breakover at 32V. I could pick the lowest breakover device out
of the bunch and maybe shave a volt or so off of that and that sorts
out the soft-trigger problem as well.

By the same strange coincidence, i brought a load of 13V zeners. They are too high to protect Lithium batteries, since I really want 12.5V. Two in series would clamp it at 26V. Zener is the same as Diacs without the negative cycle that you don\'t really need. There are many voltages to choose from as well. 12V and 13V are very common, but not 12.5V, unfortunately.
Click to expand...

Actually if memory serves me right it\'s the negative resistance aspect
of the diac which makes it ideal for driving a triac. Hopefully
someone with experience of these beasts will adjudicate the matter and
provide some clarification.
 
On Sunday, July 23, 2023 at 5:39:55 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

I need to protect some expensive RF transistors from over-voltage.
They\'re fed from a linear supply which is notorious for shorting its
pass transistors and putting 42V across these devices instead of the
required 28.5V. Until such time as I get around to finding a better
PSU, I thought the simplest expedient would be to rig up a
straightforward crowbar circuit based on sensing the voltage on the
wiper of a preset resistor in a divider chain between the 28.5V and
GND. Would this be okay for votage sensing? I don\'t really want to get
involved with op amps and precision voltage references unless it\'s
really necessary (but if it is, then so be it as these trannies aren\'t
cheap and are becoming hard to come by).
Click to expand...

Have you measured the power draw of your transmitter? Your power supply is failing because you\'re overduty-ing it. So either get a power supply rated for continuous duty at your measured power or put a duty cycle limit timer/ counter that prevents transmitter \"keying\" at excessive duty.

Do you know how to make a duty cycle limiter? A crowbar is one form but it\'s rather crude and cumbersome to work with and then you have to spend possibly hours replacing failed components. A more straightforward approach might be to thermally bond a thermistor to your power supply heat sink. All you need is repeatability, and then you can work out scaling the heat sink temp to disabling your key.


CD.
Click to expand...
 
On Mon, 24 Jul 2023 07:49:44 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 09:22:50 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmowery42@charter.net> wrote:

In article <dp4qbi5nihq1fokl0fb2jun9n4e3s0a5kr@4ax.com>,
jlarkin@highlandSNIPMEtechnology.com says...

A giant SCR crowbar would be easy. A zener and an SCR. And a fuse
maybe.




I vote for that all so for a quick fix. Simple and no adjustment.

Soft triggering an SCR, from a zener, is a potential failure mode, but
the SCR would fail shorted, which is better than blowing out the RF
stuff.

Well, by a strange coincidence I only recently bought a load of diacs
which breakover at 32V. I could pick the lowest breakover device out
of the bunch and maybe shave a volt or so off of that and that sorts
out the soft-trigger problem as well.

That\'s perfct if you can tolerate 32v. Get an SCR with an inherent
gate-cathode resistor, or just add one so the diac sees the full rail
voltage before it fires.

Diacs are wonderful gadgets. I\'ve tried to replicate the diac function
with discretes and it ain\'t easy.

An RC-Diac-LED or better yet DepletionFet-Diac-LED can make a bright
warning flasher on a high-voltage power supply that draws very little
current.
Click to expand...

35V is the absolute maximum according to the datasheet so with a
breakover of 31 or 32V I\'d feel justiified in assuming there\'s enough
headroom there to kill the supply rail before it gets anywhere close
to damaging the RF trannies.
 
On Mon, 24 Jul 2023 23:56:25 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Mon, 24 Jul 2023 07:49:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 09:22:50 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmowery42@charter.net> wrote:

In article <dp4qbi5nihq1fokl0fb2jun9n4e3s0a5kr@4ax.com>,
jlarkin@highlandSNIPMEtechnology.com says...

A giant SCR crowbar would be easy. A zener and an SCR. And a fuse
maybe.




I vote for that all so for a quick fix. Simple and no adjustment.

Soft triggering an SCR, from a zener, is a potential failure mode, but
the SCR would fail shorted, which is better than blowing out the RF
stuff.

Well, by a strange coincidence I only recently bought a load of diacs
which breakover at 32V. I could pick the lowest breakover device out
of the bunch and maybe shave a volt or so off of that and that sorts
out the soft-trigger problem as well.

That\'s perfct if you can tolerate 32v. Get an SCR with an inherent
gate-cathode resistor, or just add one so the diac sees the full rail
voltage before it fires.

Diacs are wonderful gadgets. I\'ve tried to replicate the diac function
with discretes and it ain\'t easy.

An RC-Diac-LED or better yet DepletionFet-Diac-LED can make a bright
warning flasher on a high-voltage power supply that draws very little
current.

35V is the absolute maximum according to the datasheet so with a
breakover of 31 or 32V I\'d feel justiified in assuming there\'s enough
headroom there to kill the supply rail before it gets anywhere close
to damaging the RF trannies.
Click to expand...

Is this an RF amp?

The RF guys are weird. An RF transistor might peak at 2x the supply
voltage if it\'s driving a tank. Sometimes the data sheets specify the
actual abs max, and sometimes they actually specify the max supply
voltage and assume the 2x effect. They never say.

I test them to see where they actually start to draw current.
 
On Sunday, July 23, 2023 at 2:39:55 AM UTC-7, Cursitor Doom wrote:
Gentlemen,

I need to protect some expensive RF transistors from over-voltage.
They\'re fed from a linear supply which is notorious for shorting its
pass transistors and putting 42V across these devices instead of the
required 28.5V.
Click to expand...

Well, a zener clamp is fairly easy, but you might want also to slew-limit the
voltage rise on the input; a PNP pass transistor with a little emitter-base
capacitance will filter out fast-rise edges, give a hard clamp a millisecond
to operate. With a few microseconds leeway, TL431 can implement a clamp
fairly effectively.
 
On Mon, 24 Jul 2023 15:12:08 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

On Sunday, July 23, 2023 at 5:39:55?AM UTC-4, Cursitor Doom wrote:
Gentlemen,

I need to protect some expensive RF transistors from over-voltage.
They\'re fed from a linear supply which is notorious for shorting its
pass transistors and putting 42V across these devices instead of the
required 28.5V. Until such time as I get around to finding a better
PSU, I thought the simplest expedient would be to rig up a
straightforward crowbar circuit based on sensing the voltage on the
wiper of a preset resistor in a divider chain between the 28.5V and
GND. Would this be okay for votage sensing? I don\'t really want to get
involved with op amps and precision voltage references unless it\'s
really necessary (but if it is, then so be it as these trannies aren\'t
cheap and are becoming hard to come by).

Have you measured the power draw of your transmitter? Your power supply is failing because you\'re overduty-ing it. So either get a power supply rated for continuous duty at your measured power or put a duty cycle limit timer/ counter that prevents transmitter \"keying\" at excessive duty.
Click to expand...

Well now you\'ve made an assumption there which is false. The PSU was
badly designed in the first place and is notorious for failing in this
particular piece of communications gear. In fact, rather than attempt
to repair the unit and replace the underspec components with heavier
duty ones, many repairers rip it out altogether and fit a low-noise
switcher in its stead. The orginal PSU is actually very inefficient
anyway and positively belches out heat when worked hard. Up-rating the
cooling fans is another task faced by those who choose to repair over
replacing the entire unit with a switcher. I haven\'t yet decided which
way to jump with this decision and just wanted a quick and dirty but
effective way to shut the thing off it it failed again, until such
time as I make my mind up.

Do you know how to make a duty cycle limiter? A crowbar is one form but it\'s rather crude and cumbersome to work with and then you have to spend possibly hours replacing failed components. A more straightforward approach might be to thermally bond a thermistor to your power supply heat sink. All you need is repeatability, and then you can work out scaling the heat sink temp to disabling your key.



CD.
Click to expand...
 
On Mon, 24 Jul 2023 16:17:34 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:56:25 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Mon, 24 Jul 2023 07:49:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 09:22:50 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmowery42@charter.net> wrote:

In article <dp4qbi5nihq1fokl0fb2jun9n4e3s0a5kr@4ax.com>,
jlarkin@highlandSNIPMEtechnology.com says...

A giant SCR crowbar would be easy. A zener and an SCR. And a fuse
maybe.




I vote for that all so for a quick fix. Simple and no adjustment.

Soft triggering an SCR, from a zener, is a potential failure mode, but
the SCR would fail shorted, which is better than blowing out the RF
stuff.

Well, by a strange coincidence I only recently bought a load of diacs
which breakover at 32V. I could pick the lowest breakover device out
of the bunch and maybe shave a volt or so off of that and that sorts
out the soft-trigger problem as well.

That\'s perfct if you can tolerate 32v. Get an SCR with an inherent
gate-cathode resistor, or just add one so the diac sees the full rail
voltage before it fires.

Diacs are wonderful gadgets. I\'ve tried to replicate the diac function
with discretes and it ain\'t easy.

An RC-Diac-LED or better yet DepletionFet-Diac-LED can make a bright
warning flasher on a high-voltage power supply that draws very little
current.

35V is the absolute maximum according to the datasheet so nowith a
breakover of 31 or 32V I\'d feel justiified in assuming there\'s enough
headroom there to kill the supply rail before it gets anywhere close
to damaging the RF trannies.

Is this an RF amp?
Click to expand...

It\'s the RF final output amplifier which kills the supply due to the
supply having a number of design defects. The item itself is one of
these:

https://www.universal-radio.com/catalog/hamhf/ts930s.html

The RF guys are weird. An RF transistor might peak at 2x the supply
voltage if it\'s driving a tank. Sometimes the data sheets specify the
actual abs max, and sometimes they actually specify the max supply
voltage and assume the 2x effect. They never say.
Click to expand...

Yes, they can be confusing with all that reactance to take into
account.
I test them to see where they actually start to draw current.
Click to expand...

This is where a decent VNA and a curve tracer prove invaluable. In
fact a curve tracer is one of the few pieces of test equipment I don\'t
possess. I really must get around to ordering one.
 
On Tue, 25 Jul 2023 22:52:27 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Mon, 24 Jul 2023 16:17:34 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:56:25 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Mon, 24 Jul 2023 07:49:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 09:22:50 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 23 Jul 2023 16:52:29 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 23 Jul 2023 15:20:10 -0400, Ralph Mowery
rmowery42@charter.net> wrote:

In article <dp4qbi5nihq1fokl0fb2jun9n4e3s0a5kr@4ax.com>,
jlarkin@highlandSNIPMEtechnology.com says...

A giant SCR crowbar would be easy. A zener and an SCR. And a fuse
maybe.




I vote for that all so for a quick fix. Simple and no adjustment.

Soft triggering an SCR, from a zener, is a potential failure mode, but
the SCR would fail shorted, which is better than blowing out the RF
stuff.

Well, by a strange coincidence I only recently bought a load of diacs
which breakover at 32V. I could pick the lowest breakover device out
of the bunch and maybe shave a volt or so off of that and that sorts
out the soft-trigger problem as well.

That\'s perfct if you can tolerate 32v. Get an SCR with an inherent
gate-cathode resistor, or just add one so the diac sees the full rail
voltage before it fires.

Diacs are wonderful gadgets. I\'ve tried to replicate the diac function
with discretes and it ain\'t easy.

An RC-Diac-LED or better yet DepletionFet-Diac-LED can make a bright
warning flasher on a high-voltage power supply that draws very little
current.

35V is the absolute maximum according to the datasheet so nowith a
breakover of 31 or 32V I\'d feel justiified in assuming there\'s enough
headroom there to kill the supply rail before it gets anywhere close
to damaging the RF trannies.

Is this an RF amp?

It\'s the RF final output amplifier which kills the supply due to the
supply having a number of design defects. The item itself is one of
these:

https://www.universal-radio.com/catalog/hamhf/ts930s.html


The RF guys are weird. An RF transistor might peak at 2x the supply
voltage if it\'s driving a tank. Sometimes the data sheets specify the
actual abs max, and sometimes they actually specify the max supply
voltage and assume the 2x effect. They never say.

Yes, they can be confusing with all that reactance to take into
account.

I test them to see where they actually start to draw current.

This is where a decent VNA and a curve tracer prove invaluable. In
fact a curve tracer is one of the few pieces of test equipment I don\'t
possess. I really must get around to ordering one.
Click to expand...

The RF folks should give up all that silly s-parameter and load pull
nonsense and furnish Spice models for their parts, and publish
sensible DC curves.

They usually say \"adjust the gate voltage until it works\" or something
equally scientific.

I use RF parts in time domain and have to measure things. Like
capacitances, breakdown voltages, Rds-on, pulse behavior.
 
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