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Sources of toggle switches & dc/dc solid state relays

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ron bentley
(@ronbentley1)
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@zander 

Thanks Ron, it looks like my requirement for low level dc/dc relay is a bit too ambitious, I think I will stick to the unreliable mechanical types.

Thank you for your efforts, though. Most grateful.

Ron B

Ron Bentley
Creativity is an input to innovation and change is the output from innovation. Braden Kelley
A computer is a machine for constructing mappings from input to output. Michael Kirby
Through great input you get great output. RZA
Gauss is great but Euler rocks!!


   
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Ron
 Ron
(@zander)
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@ronbentley1 Before you give up, @will turned me from a relay to a Mosfet to control 12VDC with 5VDC. I would show you a picture of the home made version I did but it is covered in hot glue now. Here is a link to a 3.3VDC/5VDC input and up to 24VDC output pre-built, but you can build your own very easily to handle more V or A if you need that. Just change the .ca to .uk.com to see if it is found, otherwise just google DAOKI or MOSFET

https://www.amazon.ca/gp/product/B07X86Y5VT/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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(@davee)
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Hi @ronbentley1,

 A look at the photo shows that the contacts of those relays are 10A 28Vdc, assuming they are 'genuine' ratings.

The 10A rating is based on a 'resistive' load, which is the 'least demanding' type of load. From memory, 'professional' relays with 10A contacts would typically derate to about 2A rating when faced with capacitive or inductive loads.

But your reports of frequent failures is concerning, albeit I am assuming the failures are contacts which are burnt and/or welded together, rather than more unusual problems due to to poor manufacture, etc.

I which case I can only imagine the currents being switched are significant, possibly exacerbated by arcing when the contacts open and large voltages are developed.

--------

In short, I don't really know how to proceed without a more precise electrical specification of what you need.

--------

Looking at the problem from the other direction .. what devices are available?

There are many boards with 4 to 8 'ssr' s, at least some of which can probably be driven by an Arduino. However, the majority of those I looked at were clearly aimed at 200-300V AC, and are unsuitable for your application. To complicate matters, many have abysmal specifcation/descriptions .. and judging by the reviews I clicked on, others have been caught out.

e.g. //www.amazon.co.uk/dp/B07QQMNBJZ/ref=sspa_dk_detail_4 

DollaTek 5V 8-Channel Solid State Relay High Level Trigger SSR Module Board for Arduino ARM DSP PIC With Resistive Fuse

looks hopeful until you look at the translated review

The board works great, it consumes little, and the switching is instant. The problem is that if, as in my case, you want to drive devices (solenoid valves) at 12 volts, you can't do it. In fact, the card is designed to drive devices at 230 VAC. Luckily I had another one that was driving 230 VAC electric shutters and replaced it with that. Once we know this... five stars without a doubt

I suspect the same applies to the board @zander showed, but the description is ambiguous and I can't see the type number on the individual modules to be sure.

------

There are more hopeful looking examples - e.g. https://www.aliexpress.com/item/32848618783.html

8 road solid state relay module /9V/12V/24V output / controllable solenoid valve / small motor /LED lamp and so on

The specification on the web site leaves much to be desired, but the switches are only 2A, so the lack of requirements specification means I can't even be sure that their life will be as long as your relays.

---------------------------------------

Summarising the story so far:

It is likely there are solutions 'out there'.

Some are available as convenient units with 4-8 on a module - but many may be 'singles' that need soldering to a board

They may be more expensive than the more obvious, but unsuitable types

The absence of a specification makes choosing like the national lottery ... if you buy a ticket, you might win .. but the probability of not winning is a lot higher.

-----------

Best wishes, Dave


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 3 years ago
Posts: 6662
 

@davee The board I am showing as well as the similar board i made is driving 12VDC.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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ron bentley
(@ronbentley1)
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@davee 

Thanks Dave for you focussed interest and assistance.

I've come to the conclusion to stay with the mechanical relays, these at least do what I want.

Many thanks

Ron B

Ron Bentley
Creativity is an input to innovation and change is the output from innovation. Braden Kelley
A computer is a machine for constructing mappings from input to output. Michael Kirby
Through great input you get great output. RZA
Gauss is great but Euler rocks!!


   
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(@davee)
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Hi @ronbentley1,

  @will & @zander have come up with a picture of a boards from Amazon .. I can't see the reference as it's been eaten by the Kindle preview bug ... but I found a similar looking board:

//www.amazon.co.uk/AZDelivery-IRF520-Driver-Module-including/dp/B07191NYQH/ref=sr_1_17

Unfortunately my 'review' of it is rather technical, and has morphed into another sermon ... if it looks scary, jump to the Summary near the bottom!

---------------------

This board is essentially a 'bare' IRF520 MOSFET, with screw terminal connections.

In fact all of the possible "SSR" s I found are based on MOSFETs, which is not great surprise as SSR is really is misnomer, as there is no relay! I suspect the MOSFETs on the board I found had quite different characteristics, which might have made them more 'Arduino' friendly, but also meant that were smaller, lower current devices. They were also more expensive!

----------

Because its a single n-channel FET, the only 'practical' place for it is with the source connection connected to 0V (ground). This means the +12 V line must be directly connected to the load, and the FET will be switching the 0V return line.

This is not the 'intuitive' approach, since it has disadvantages due to the circuit always being 'live'.

The only common case of  this approach that I can think of, is the 'push to open' switch used in car doors that switches on the interior light when the door is opened ... this works by connecting the 'low' side connection of the light to the car chassis when the door is open, and no longer pushing the switch open.

It is possible to devise extra circuitry to get around this limitation, but it is not trivial.

--

The board does not have any diode component to protect against back emf transients, although FETs do have an intrinsic avalanche diode, and that may be sufficient, so I'll give it 'the benefit of the doubt' for now.

---

The IRF520 is a higher current FET (than those in the board I found), rated at over 5A continuous.

However, to achieve this rating the gate (relative to source) drive voltage needs to be around 10V.

Most Arduinos will only achieve just under 5V, and the ESP32/ESP8266 (plus some Arduinos), just under 3.3V.

This means ESP32, etc is a non starter, and 5V Arduinos are a very poor and unreliable match. I'll explain in more detail below.

---------

Driving an IRF520 with an Arduino is very poor design technique. (Some MOSFETs are designed to be controlled by logic devices, such as Arduinos --- the IRF520 is definitely not in that group!!)

The exact performance of each board will be a lottery, as this MOSFET has wide tolerances on its characteristics.

The full data sheet of the original Internatoinal Rectifier device is at

http://www.irf.com/product-info/datasheets/data/irf520.pdf

Pertinent extracts include:

image
image

The table Vgs - gate source threshold states the drive voltage range needed to make the FET pass a small current (0.25 mA) , which it lists as 2.0 V to 4.0 V.

Vgs is the voltage needed to pass a very small current .. maybe enough to make a small RED LED show a slight glow. The principle being, if you drive with a voltage of less than this value, the current passed by the FET will be 'negligible', bearing in mind it is 'power' device, designed for several Amps of current.

The range of 2.0 V to 4.0 V is the 'lottery' variation .. each device will be different. However, if you were driving with an ESP32 (say), whose maximum output voltage is under 3.3 V, then a device with this threshold voltage near 4.0 V, would not even be able pass enough current to cause a small LED to glow!

The graph shows another side of the same problem, although it is more difficult to interpret.

Each plotted line on the graph is the maximum current the FET will pass for a given gate-to-source drive voltage against voltage from drain-to-source. (Note that each line initially increases with increasing voltage, then reaches a maximum current level.)

All of the lines on the graph refer to a 'typical' device .... which we might guess means its threshold voltage just discussed is in the middle of the extremes .. say at 3.0 V.

The lowest curve is when the voltage applied to the gate, relative to the source of 4.5 V ... which shows a maximum current of about 1 A.

The maximum voltage from a 5 V Arduino will probably be about 4.9 V, so if you have a 'typical' FET the maximum current you will be able to supply to your load will be just over 1 A. Any attempt by the load to demand more current will cause the FET to reduce the voltage to the load, the FET itself will get hotter, so the power supplied to the load will be roughly constant.

If your board had threshold near to 4V, I would guess/estimate the maximum current level that could be achieved with Arduino control could be as low as 0.25 A ...

-----------------------

In summary:

To make this board generally usable and reliable it needs an interface circuit to 'boost' the drive voltage to about 10V. Without this 'boost':

  • this board is totally unsuitable for connecting to ESP32/ESP8266, (plus the rarer 3.3V Arduinos)
  •  
  • With a 5V Arduino, the maximum current some boards will deliver may be as low 0.25 A. This limit depends upon 'luck of the draw' ... i.e.  the individual FET characteristics and its temperature.
  •  
  • This board can only be connected on the 0V side. That is the +12 V line would be permanently connected to the load. This 'switch' is inserted between the '0V' (low side) connection of the load, and the '0V' connection of the supply. (A simple 'boost' board would not remove this limitation, although an alternate, more complex circuit could be devised.)

Describing this as a device that can deliver 1 A or more relies on hoping you get a 'good' set of boards.

Bear in mind a batch of boards may all use MOSFETs from the same silicon wafer and may have similar characteristics .. it is plausible to buy 100 boards and they are 'all good' or 'all bad'.

 Do you feel lucky?

----------------------

But of course, presently we don't know what current your load needs ... so even 'good' boards may not be 'good enough' (and vice versa).

-----------------------

Sorry to be so negative ... hope you find a solution ... I am not sure I can help much more without some 'hard facts' about your system. If you find some more information, solutions are available, although some construction might be required.

Best wishes, Dave


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 3 years ago
Posts: 6662
 

@davee Very thorough as always Dave. I also share your concern re the circuit being 'live'. However, I have one purchased module, and one I made from components. They are working just fine. The key point for the OP is how much current is needed. In my case it was a 15W LED strip, but it's cut into about 10ft and 5 ft so the worst case is the 10ft at about 10W. Since I am using a 12V supply that is about 830 ma for the bigger length. 

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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ron bentley
(@ronbentley1)
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@davee 

I have a sneaky feeling that you have rather enjoyed this strand of research!

I am sorry that my request for advice has exploded into such a broad set of considerations and concerns. I am not well versed in electronics or its theory and I can now see that my call out for advice was a wise one.

There are, clearly, many things to consider in this instance, far more than I would wish to explore in depth at this point

If I have learned anything it is:

  1. Dont assume anything
  2. Challenge everything, and
  3. Dont be afraid to seek advice

I am most grateful for your interest in my query and for your tenacious approach researching.

I shall close this thread down and crawl back into my hole and wait for my next good idea! Ha , ha.

In all seriousness, thank you, and others, for your inputs.

Cheers

Ron B

 

 

Ron Bentley
Creativity is an input to innovation and change is the output from innovation. Braden Kelley
A computer is a machine for constructing mappings from input to output. Michael Kirby
Through great input you get great output. RZA
Gauss is great but Euler rocks!!


   
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frogandtoad
(@frogandtoad)
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Posts: 1458
 

@ronbentley1 

Hi Ron,

FYI: - A quick search for micro, miniature toggle switch SPST PCB mount or "sub miniature" will yield plenty of results on eBay, Amazon and other web search results.

I have also come across some "latching" breadboard push button switches in the past, if that is an option.

Alternatively, one of Bills recent video's on the 555 timer with a push button might just do what you want.

Cheers and good luck!


   
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ron bentley
(@ronbentley1)
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@frogandtoad 

Hi,

Thanks for your post, but I still cannot locate a suitable item!

All of the on/off toggle switches I have seen will not fit a breadboard, but are panel mounted.

I seem to have, what seems to me anyway, an unreasonable requirement!

If we take a simple button switch, breadboard suitable, and replace the button with a toggle lever then that's what I am seeking.

However, your suggestion about a latching button switch is a good one, providing they come breadboard compatible. I will chase this up

Many thanks for your efforts and post.

Cheers

Ron B

Ron Bentley
Creativity is an input to innovation and change is the output from innovation. Braden Kelley
A computer is a machine for constructing mappings from input to output. Michael Kirby
Through great input you get great output. RZA
Gauss is great but Euler rocks!!


   
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Inst-Tech
(@inst-tech)
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Posts: 554
 

@ronbentley1 Hi Ron, take a look at these,

 

https://www.amazon.com/microtivity-IM211-Push-Button-Switch/dp/B006S21U2G

they appear to be what your looking for...here a video I found showing them used ion a bread board..

regards,

LouisR

LouisR


   
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ron bentley
(@ronbentley1)
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@inst-tech 

Hi LouisR,

Thanks for your post.

Yes these seem to be what I was looking for, thank you.

The video was helpful, but unfortunately the amazon link didnt show.

Interestingly enough, another fellow  member came up with the same suggestion.

I will chase this up.

Thank you.

Regards

Ron B

 

Regards

Ron Bentley
Creativity is an input to innovation and change is the output from innovation. Braden Kelley
A computer is a machine for constructing mappings from input to output. Michael Kirby
Through great input you get great output. RZA
Gauss is great but Euler rocks!!


   
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frogandtoad
(@frogandtoad)
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Posts: 1458
 

@ronbentley1

Posted by: @ronbentley1

However, your suggestion about a latching button switch is a good one, providing they come breadboard compatible. I will chase this up

Many thanks for your efforts and post.

Ron... I am sure you will find something suitable!

Cheers


   
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ron bentley
(@ronbentley1)
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Topic starter  

Thanks to everyone who has contributed to my post, it's been ..... interesting.

My latching button switches (toggles) arrive today! The video was most helpful plus the other links you have provided.

Many thanks

Ron B

Ron Bentley
Creativity is an input to innovation and change is the output from innovation. Braden Kelley
A computer is a machine for constructing mappings from input to output. Michael Kirby
Through great input you get great output. RZA
Gauss is great but Euler rocks!!


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 3 years ago
Posts: 6662
 

@ronbentley1 I should have thought of the latching button since I have them on 

https://www.amazon.ca/gp/product/B07L84QZTY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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