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Author Topic: simple junkbox sequencer experiment.  (Read 2338 times)
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Opcom
Patrick J. / KD5OEI
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« on: February 24, 2023, 06:18:15 PM »

No messy op-amps, FETs, ESD-sensitive parts, microcontrollers, and no baroque masterpieces. Just regular cheap transistors and zener diodes that are not critical, and the simplest circuit with reasonable timing and hackability.

Saw this and didn't want to go hunting ICs and MOSFETs not on hand, but then saw that it's just like an LED bar graph.
https://vhfdesign.com/wp-content/uploads/2016/06/sequencer-schema.png

A ramp turns on the relays in order as it rises, and then as it falls turns it them off in reverse order.

No frills, just relays could be operated as 1-2-3-4-5__5-4-3-2-1.
LTspice looks OK, maybe I will play with it later.


* LTspice sequencer experiment.pdf (146.18 KB - downloaded 130 times.)
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km6sn
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« Reply #1 on: February 24, 2023, 11:55:36 PM »

This  task is ideally suited for an ATmega328 or a PiZero., or even a PiNano at
$4 from Adafruit.

Using any of the above you could change the timing and/or sequences via a serial port. I am sure there is freeware out there for this purpose.

A more advanced technique would be to have multiple sequences to
accommodate different amplifiers, etc.

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w9jsw
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« Reply #2 on: February 25, 2023, 08:18:46 AM »

I like it!

I built a simple 2 stage sequencer using 2 relays and a cap. Works well on my 813 rig. No sparks. But this one is one I will keep in mind.

I wrote a sequencer in Arduino code and had it running. What stopped me is 2 things -

1. If it breaks in 5 years, will the IDE and hardware still be available to repair it. Will I remember how to repair it? Will parts be unobtanium like the relay board or the CPU. Will i still have the code or will it get lost on an old laptop that crashes.

2. Practically speaking, if the transmitter goes to another person instead of being scrapped when I die, will they be able to maintain it.

So, KISS, I used a simple relay circuit that anyone can figure out.

John
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Opcom
Patrick J. / KD5OEI
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« Reply #3 on: February 28, 2023, 12:26:48 AM »

I like it!

I built a simple 2 stage sequencer using 2 relays and a cap. Works well on my 813 rig. No sparks. But this one is one I will keep in mind.

I wrote a sequencer in Arduino code and had it running. What stopped me is 2 things -

1. If it breaks in 5 years, will the IDE and hardware still be available to repair it. Will I remember how to repair it? Will parts be unobtanium like the relay board or the CPU. Will i still have the code or will it get lost on an old laptop that crashes.

2. Practically speaking, if the transmitter goes to another person instead of being scrapped when I die, will they be able to maintain it.

So, KISS, I used a simple relay circuit that anyone can figure out.

John

=====================

John, this was exactly my consideration and purpose -simple, hackable analog computing based on easy to use and easy to substitute parts. Large relays or contactors can also be directly controlled if the transistor is sized up or a big one added, Darlington style.

I admit my circuit is more complicated than 2 relays and a cap. I had a concern that the cap could change value too much with time, or would have to be re-selected if the relay was changed. It's not that a big concern as long as good parts are used.

I only need 3 stages to avoid hot-switching the amplifier's TR relay. 5 were drawn because it was simple to just add more and see how far it could go.  

Diode logic added to program the more elaborate sequences could be a thing with this, as could a small diode matrix as a state ROM (for example to program out-of-order operation), but I don't need it for my uses. It could be a fun LTspice experiment to investigate that.

Maybe the use of fundamental voltages, currents, and hardware to program the functions of other hardware is a lost art, but I hope not. I considered 2D21s just for kicks, but turning them off would have required AC power or a reset pulse / more relays, so I didn't explore that which wasn't needed. Didn't want to go into baroque territory.

Some sequences may require elaborate or precise functions that require a microcontroller. I guess it also depends on the individual preference.

KISS principle.

Patrick
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w9jsw
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« Reply #4 on: February 28, 2023, 07:37:54 AM »

My relay sequencer is based on this article but scaled for my 24V control voltage. The second pic is a snip of my actual sequencer. The third relay is used to actuate my exciter. Basically everything except the antenna is wired together.

* 2 relay sequencer.pdf (293.72 KB - downloaded 71 times.)

* Sequencer.jpg (80.27 KB, 758x667 - viewed 178 times.)
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Opcom
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« Reply #5 on: February 28, 2023, 10:27:33 PM »

That's a great hookup and easily worked with.

In your schematic, what are "-Rest-Enable" and "To SDR CW Enable" ?

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w9jsw
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« Reply #6 on: March 01, 2023, 06:46:09 AM »

Everything is negative enabled by grounding. -rest-enable is "the rest of the signals, such as plate enable, mod enable, hv enable, exciter enable, snuffer disengage, etc. -Ant-enable only handles the antenna. I bring up everything at once, however the HV has a step start so it lags a bit. The snuffer is a NC vac relay and a 3.5k resistor that is placed across the mod trans secondary to quench any voltage there after a QSO. A K1JJ idea.

The relay for the exciter feeds "to SDR CW Enable" It is just a pair of contacts that close. On my Hermes Lite, while in any mode, if you close the CW key input, it will emit a CW tone at the current TX frequency. I have the SDR in AM mode and when I want to TX, I close the CW key input with this relay to cause the SDR to transition to TX and drive the 813 rig.
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K8DI
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« Reply #7 on: March 01, 2023, 08:05:19 AM »

The relay for the exciter feeds "to SDR CW Enable" It is just a pair of contacts that close. On my Hermes Lite, while in any mode, if you close the CW key input, it will emit a CW tone at the current TX frequency. I have the SDR in AM mode and when I want to TX, I close the CW key input with this relay to cause the SDR to transition to TX and drive the 813 rig.
As you’re probably aware, lots of modern radios have features that accomplish the same feat.  I use a Yaesu FT 991A in AM mode to receive and its linear amp tuning feature to transmit with the RCA conversion.  The tune feature is for the linear to invoke a CW tone for tuning the linear while the radio is in other modes, with the power level as set in CW mode…meaning when I crank it to 100w on SSB, the 21 watts I need to excite the rig stays 21 watts…makes life easy. I activate it with a contact closure, although in the case of the RCA the relay is part of a control system that does a bunch of other stuff too.

I used a pair of relays, diodes, resistors, and caps to sequence  my first home brew rig, 6CA7’s modulating an 807, with zero problems. And, as said, anyone can figure it out.

On that note of “figure it out”, I’ve begun taping/attaching plastic page protectors with notes and drawings/schematics to the inside of my modified or homemade gear. I’m already aware I forget stuff…and when I’m mentally done, it will help the next guy use it rather than scrap it.

Ed
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km6sn
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« Reply #8 on: March 02, 2023, 01:14:53 AM »

r.e. concerns for microprocessor software development tools availability

There are software development tools available still today for the 8080 and Z80 processors. Those micros are 45 years old.

The  Arduino Uno Atmega 328p boards are so powerful and so ubiquitous it is hard for me to imagine software tools for them going away in the next 30 years.

And the  only hardware development environment needed is a USB cable, and they are likely to be around for some time yet.
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« Reply #9 on: March 02, 2023, 10:20:34 PM »


or there is this:

https://www.downeastmicrowave.com/product-p/ltrsb.htm

gl

/dan
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Opcom
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« Reply #10 on: March 05, 2023, 07:24:01 PM »

The nice thing about op-amp versions is the ramp voltage can be very modest for the same granularity of the timing control.
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