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[SOLVED] Where to purchase SMD relays

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ljcox

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I need relays with the following specifications:-
A coil voltage in the range 5 Volt to 48 Volt.

Contacts - either DPST or DPDT able to switch at least 60 Volt DC and a current rating of at least 500 mA.
I prefer SMD mounting but through the hole will suffice if SMD relays with the above specifications are not available.

Does any one know where I can purchase such relays? I need 80, so the price is critical.

I tried RS Components & Element 14, but they have little to offer.

I also did a search of Chinese companies but found their web sites frustrating. The ones I viewed did not have a sensible search engine. Besides, I have the feeling they don't want enquiries from the likes of me.

Any assistance will be appreciated.
Len
 

Hi,

My first way is to go to the manufacturer's internet site and look for distributors.
The next is the distributor's internet site.

I wonder why you say more than 100 different types (I found) at element14: "they have little to offer".
How many do you expect?

Isn't 10 different types you can choose more than enough?

Klaus
 

Digikey has bunches. But could you use a couple of mosfets?
 

Klaus,
Thanks for the response. I tried the manufacturer's web site did not think of looking for the distributors.

What I meant by "E14 have little to offer" is that although some were technically suitable, they were all too expensive. Remember that I need 80 relays

- - - Updated - - -

Barry,
Thanks for the response.

I initially did the design using MOSFETs but I needed 2 protection diodes per MOSFET which means 160 diodes.

Whereas, relay contacts don't need protection.

Len
 

Hi,

You have marked this thread as solved, therefore don´t expect (much) new resonse.

I initially did the design using MOSFETs but I needed 2 protection diodes per MOSFET which means 160 diodes.
Click to expand...

* There are packages with multiple mosfets inside. There are packages with multiple diodes inside.
* for driving a relay you should consider to add a free wheeling diode across the coil. So you don´t safe part count.

Whereas, relay contacts don't need protection.
Click to expand...
Are you sure?
True if you are within relay contact specification,
But this is true also for mosfets....no external protection needed if the signals are within mosfet specification.

But I have to admit: relay contacs in general are less sensible against overvoltage/overcurrent.

Klaus
 

ljcox said:
Klaus,
Thanks for the response. I tried the manufacturer's web site did not think of looking for the distributors.

What I meant by "E14 have little to offer" is that although some were technically suitable, they were all too expensive. Remember that I need 80 relays

- - - Updated - - -

Barry,
Thanks for the response.

I initially did the design using MOSFETs but I needed 2 protection diodes per MOSFET which means 160 diodes.

Whereas, relay contacts don't need protection.

Len
Click to expand...
2 diodes plus a mosfet is WAAAAAY cheaper than any relay you'll find.
 

Klaus,
I know I'll need diodes across the coils. What I mentioned was there is no need to protect the contacts since there will never be a current through them when the open or closed. There will only be current through them occasionally for about 10 ms while the contacts are closed.

Many years ago, I worked on the design of complex relay systems, and in some cases, I designed interfacing electronic logic to the relays.

Barry,
What I need is a latching relay or the electronic equivalent. I'm still exploring the options. One possibility is to use 2 optically coupled MOSFETs,

Thanks for the responses.
Len
 

ljcox said:
I need relays with the following specifications:-
A coil voltage in the range 5 Volt to 48 Volt.

Contacts - either DPST or DPDT able to switch at least 60 Volt DC and a current rating of at least 500 mA.
I prefer SMD mounting but through the hole will suffice if SMD relays with the above specifications are not available.

Does any one know where I can purchase such relays? I need 80, so the price is critical.

I tried RS Components & Element 14, but they have little to offer.

I also did a search of Chinese companies but found their web sites frustrating. The ones I viewed did not have a sensible search engine. Besides, I have the feeling they don't want enquiries from the likes of me.

Any assistance will be appreciated.
Len
Click to expand...

Check the following relay at Farnell. It is THRU HOLE and over rated to your specs, but available in QTY more than 1000 pieces.

https://uk.farnell.com/axicom-te-co...01/relay-signal-dpdt-250vac-220vdc/dp/1174991

Manufacturer: AXICOM - TE CONNECTIVITY
Order Code: 1174991
Contact Configuration: DPDT
Coil Voltage: 48VDC
Contact Current: 3A Product
Range: D2n/V23105 Series Relay
Mounting: Through Hole
Coil Type: Non Latching
Contact Voltage VAC: 250V
Relay Terminals: Solder
Contact Voltage
VDC: 220V
Contact Material: Silver Nickel Coil
Resistance: 4kohm
 
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    ljcox

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Thanks for that, but it is too expensive since I need to buy 80 of them.

I have attached the 2 of the options I have been considering.

Any comments or suggestions will be welcome.

Len
 

Attachments

  • Options.jpg
    Options.jpg
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There may be a high power IC similar to 4066 (quad bilateral switch). When you apply voltage to a gate terminal, it passes analog signals in either direction.
 

I have attached the 2 of the options I have been considering.
Click to expand...
Seeing this circuits, I don't understand why you consider a double throw relays or respective electronic switches. I only see a SPST switch function and a hold logic function that can be well implemented by means of switch control. Thus you are talking about a single floating 60V/500 mA switch, apparently unipolar plus respective control logic.

I initially did the design using MOSFETs but I needed 2 protection diodes per MOSFET which means 160 diodes.

Whereas, relay contacts don't need protection.
Click to expand...
I generally disagree. Both may work without or need protection circuitry, depending on the load and expectable maximum voltage.
 

FvM, Thanks for the response but I don't understand it.
What do you mean by"double throw relays" The circuit shows a DPST relay.
And in this sentence "I only see a SPST switch function and a hold logic function that can be well implemented by means of switch control" what do you mean by "switch control"

BradtheRad, Thanks for that thought. Certainly a high voltage, high current analogue switch would be excellent. Perhaps someone will know of one.

Len
 

FvM, Thanks for the response but I don't understand it.
What do you mean by"double throw relays" The circuit shows a DPST relay.
And in this sentence "I only see a SPST switch function and a hold logic function that can be well implemented by means of switch control" what do you mean by "switch control"
Click to expand...
My fault, the circuit actually uses DPST rather than SPDT.

The more important point is however that one of the two contacts is only used for a coil hold function and doesn't need 60V or 500 mA rating. I suggested to implement a logic hold function instead.
 

How about you simply suggest a price that is not too expensive?
How much are you willing to spend per relay?
 

Thanks for all of the suggestions.
After much consideration of the various options, I decided to avoid relays & do the holding function in the PIC.
I had intended to use a pair of 16F684 PICs but this PIC does not have enough input/output pins.
So I will use the 40 pin 16F877. The software will be more complicated as it only has 4 RB change inputs.
Len
 

Um, your PIC is not going to be able to handle 500ma at 60 V. Looks like you're back to your original question. And it's not clear what's going on here. In your sketch in post #9 where's the load? You show a DPST relay shorted together making it SPST. And your diode to "prevent positive pulses" is paralleled by a resistor that will conduct positive pulses.

I think we need a better explanation of what you're trying to do here.
 

barry said:
Um, your PIC is not going to be able to handle 500ma at 60 V. The inputs have 100k resistors in series to protect the PIC inputs. Looks like you're back to your original question. And it's not clear what's going on here. In your sketch in post #9 where's the load? The point is to apply a 0V to the P wire when necessary. You show a DPST relay shorted together making it SPST. No, it is a DPST - only the lever springs are connected together. And your diode to "prevent positive pulses" is paralleled by a resistor that will conduct positive pulses. Yes, but the resistor will be 100k also.

I think we need a better explanation of what you're trying to do here.
Click to expand...

Thanks for the comments Barry. My comments are in red.

The attachment shows how I was intending to do it using a 16F876 PIC. Since then I conceived a better way to do it hence the enquiry about obtaining relays.

But, as I said in post 16, I will do the "holding function" in software.

The attachment did not employ the "holding function". It had 2 "release" inputs - see the left hand side.

Normally the P wires are open. When 0V appears on one of them, the PIC waits until it is removed & then, after a delay of 30 ms, it applies a 0V to the P wire (by turning on the respective MOSFET) until the release pulse is detected. Then it removes the 0V from all P wires & returns to the initial state.
In the improved version, the P wire 0V potentials are kept on until the Holding 0V is removed. If I used a relay as in post 9, the relay would release when the holding 0V is removed.
But now, as I said, I'll do all of this in a 16F877 PIC.
Len
 

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Last edited:

KlausST, You said in Post 5 "There are packages with multiple diodes inside"
I have been searching for such devices without success. The best I could find was packages with 2 diodes inside. I would prefer more. Ideally 6 diodes with a common cathode. Or one with 6 individual diodes.
Alternatively, if these are not available, then a 3, 4 or 5 diode package would suffice.
Any assistance will be appreciated.
Len
 

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