Running 5V solenoid straight off of Pi using a relay

[sgraphics]

Hi,

I'm new to this and would like to validate a scenario before doing anything. I already managed to fry one Pi last month

Can I run a 5V solenoid straight off of Pi using a relay (without additional breakout board, diodes or transistors)?

Products:
Board: Raspberry Pi 4B
Solenoid: https://www.adafruit.com/product/3992
Relay board: https://thepihut.com/products/raspberry-pi-relay-board

By default they propose this setup: https://cdn-shop.adafruit.com/product-f ... driver.pdf ("These draw quite a bit of current, 800mA at 5V and 1 Amp at 6V so you'll want a good strong driver.")

But would this set up work? As I understand Pi as well has 5V outs, so why not drive it directly?

solenoid.png (7.04 KiB) Viewed 489 times

[pcmanbob]

Hi.

Yes the relay board will work correctly with the pi no other components required,

As to powering the solenoid directly from the pi ,

it will depend on how go the power supply is you are powering your pi from , and what else is drawing power from the 5V rail ( your relay board for example ).

You may find that when you activate your solenoid you pi crashes or even reboots due to the sudden load place on the 5V rail .

If this happens you will need a separate power supply for the solenoid.

Your diagram is also wrong this is how it should be connected, and I recommend a diode be connected as shown to protect the relay contacts from the reverse voltage spike on solenoid power off.



connections to the gpio pins to control the relays are made by the fact that the relay board plugs directly on to the pi gpio pins.

[sgraphics]

Thanks for the reply! I cannot see the images you posted though - they dont seem to be loading

[pcmanbob]

Thanks for the reply! I cannot see the images you posted though - they dont seem to be loading

I never normally have any problems with posting images on the forum, I do it all the time.

but here are direct links to them.

https://i.imgur.com/Tb542KV.jpg

https://i.imgur.com/4Aa4Vox.jpg

which I checked and work so if you still cant see them the problem is at your end

[sgraphics]

Hi, you are right problem was on my end (proxy). Thanks for the thorough explanation!

[sgraphics]

Btw, can I use a 1N4007 (1N4007 Si-D 1000V 1A) diode instead of a 1N4001 one for the safety? Can't seem to find 1N4001 anywhere locally..

[mahjongg]

Btw, can I use a 1N4007 (1N4007 Si-D 1000V 1A) diode instead of a 1N4001 one for the safety? Can't seem to find 1N4001 anywhere locally..

Yes, the 1N4007 just is able to withstand a higher reverse voltage (1000V) than the 1N4001.

[emma1997]

I don't think a single 1n4001 has been manufactured in decades. They may be marked 1n4001 or 1n4002 or 1n4004 etc but in fact all are 1n4007 die relabeled. This was confirmed in an EEVblog thread few years back where many samples from many sources were characterized and compared with vintage parts. Conclusion was the last time real 1n4001 were made and sold was about 20yrs ago and at that time they actually cost more than 1n4007.

With modern transistors and proper software it's debatable whether EMF diodes are needed and in fact much evidence indicates can do more harm than good.

[drgeoff]

With modern transistors and proper software it's debatable whether EMF diodes are needed and in fact much evidence indicates can do more harm than good.

Even if your assertion were true (which is another argument I'm not starting) the diode that pcmanbob advocates is protecting relay contacts not transistors.

[mahjongg]

The diode prevents a very high voltage over the coil when current through the coil is abruptly shut down.
It depends on what is connected to the coil ends if the diode is removed what will be blown up, but I have learned that it is most often the transistor that tries to switch off the current that is the victim, but if the coil current is switched with relay contacts you are right.

[PeterO]

As a matter of principle I would never drive any large inductive load like a solenoid from the Pi's 5V supply.
PeterO

[pcmanbob]

If you have ever looked at a set of relay contact that have been switching an inductive load you would see how much damage they can suffer.

That's why I suggested the diode.

[pcmanbob]

As a matter of principle I would never drive any large inductive load like a solenoid from the Pi's 5V supply.
PeterO

I did say it was not recommended, but I guess the OP can do what they wish its their pi to damage.

[PeterO]

As a matter of principle I would never drive any large inductive load like a solenoid from the Pi's 5V supply.
PeterO

I did say it was not recommended, but I guess the OP can do what they wish its their pi to damage.

I'm agreeing with you so not sure what your "I did say....." is about ?
PeterO

[Brandon92]

I'm also wondering if the inrush current of that solenoid will be a problem for the Rpi. This may give a "large" voltage drop in the 5V rail and the Rpi doesn't like that.

[PeterO]

I'm also wondering if the inrush current of that solenoid will be a problem for the Rpi. This may give a "large" voltage drop in the 5V rail and the Rpi doesn't like that.

A solenoid is an inductor not a capacitor !

PeterO

[Brandon92]

I'm also wondering if the inrush current of that solenoid will be a problem for the Rpi. This may give a "large" voltage drop in the 5V rail and the Rpi doesn't like that.

A solenoid is an inductor not a capacitor !

PeterO

Indeed, I think I need to go to bed