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by emma1997
Fri Nov 20, 2020 2:11 am
Forum: HATs and other add-ons
Topic: Relay' connected to Rpi Zero W - causes it to freeze
Replies: 51
Views: 7121

Re: Relay' connected to Rpi Zero W - causes it to freeze

IIRC tlfong01 was "gravely reprimanded" for posting "very colorful" * post, which may have irritated some forum members and/or mods Whaaaa???? Nahhh... that don't sound like this forum. lol I do miss being ...
by DougieLawson
Thu Nov 19, 2020 10:13 pm
Forum: HATs and other add-ons
Topic: Relay' connected to Rpi Zero W - causes it to freeze
Replies: 51
Views: 7121

Re: Relay' connected to Rpi Zero W - causes it to freeze

IIRC tlfong01 was "gravely reprimanded" for posting "very colorful" * post, which may have irritated some forum members and/or mods from then on... no more contributions from tlfong01.... * literally, as ...
by LTolledo
Thu Nov 19, 2020 10:07 pm
Forum: HATs and other add-ons
Topic: Relay' connected to Rpi Zero W - causes it to freeze
Replies: 51
Views: 7121

Re: Relay' connected to Rpi Zero W - causes it to freeze

He might be still here, but only "lurking", he has not posted here since that last post in 2018. IIRC tlfong01 was "gravely reprimanded" for posting "very colorful" * post, which may have irritated some forum members and/or mods from then on... no ...
by tlfong01
Mon Mar 11, 2019 7:15 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 6753

Re: I2C I/O PORT EXPANDER QUESTION

... (and LED) value from 1k to 6k to make 5V Logic also 3V3 compatible is a general trick that applies to opto or direct, high trigger or low trigger relay, or power MOSFET or BJT as a sinking source driver. An example is the following SainSmart opto low trig relay. The original in1 is Arduino compatible ...
by tlfong01
Fri Mar 08, 2019 12:56 pm
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 6753

Re: I2C I/O PORT EXPANDER QUESTION

tlfong01 wrote:
Fri Mar 08, 2019 8:59 am
NE555 > ULN2803 > Songle 5V Relay > DC12V Motor Tested OK


NE555 > ULN2803 > Songle 5V Relay > DC12V Motor Schematic
...
by tlfong01
Fri Mar 08, 2019 8:59 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 6753

Re: I2C I/O PORT EXPANDER QUESTION

tlfong01 wrote:
Fri Mar 08, 2019 8:02 am

NE555 drives ULN2803, which drives Songle 5V Relay - Tested OK

https://youtu.be/KpE9n6SSraU (youtube)
...
by tlfong01
Fri Mar 08, 2019 6:35 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 6753

Re: I2C I/O PORT EXPANDER QUESTION

tlfong01 wrote:
Fri Mar 08, 2019 4:56 am
I am using TK73-424 Quad Songle relay which is cheaper than Omron.


TK73-424 Songle Relay Inductance Measurement Resutls

I measured the inductance of the 4 Songle relays, and found them almost identical, about 40mH.
...
by tlfong01
Fri Mar 08, 2019 4:56 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 6753

Re: I2C I/O PORT EXPANDER QUESTION

tlfong01 wrote:
Thu Mar 07, 2019 2:55 pm

How deep is your pocket?

Another usual user requirement is "As cheap as possible". I am a poor hobbyist, so I also have this requirement. I am using TK73-424 Quad Songle relay which is cheaper than Omron.
...
by tlfong01
Thu Mar 07, 2019 7:57 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 6753

Re: I2C I/O PORT EXPANDER QUESTION

(1) PCA9865 is only TTL 25mA output only, not strong enough to control a 5V relay which needs 70mA. You may need stronger switches such as ULN2803. (2) Rpi GPIO is only 3V logic. You might need to consider using logical level shifter to convert the signals to ...
by tlfong01
Wed Mar 06, 2019 2:33 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

tlfong01 wrote:
Tue Mar 05, 2019 1:10 am
tlfong01 wrote:
Mon Mar 04, 2019 6:18 am
No flyback diodes across relay switch


ULN2803 Output Clamp Diode passes relay flyback current

ULN2803A Darlington Transistor Arrays Datasheet - TI
http://www.ti.com/lit/ds/symlink/uln2803a.pdf
...
by tlfong01
Wed Mar 06, 2019 2:04 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

tlfong01 wrote:
Wed Mar 06, 2019 6:29 am
Songle 5V Relay Inductance ~= 40mH

Songle 5V Relay Toggling at 1 Hz

Songle relay 2019mar0601
https://youtu.be/XZxZ5fhoK9o (youtube)
...
by tlfong01
Wed Mar 06, 2019 11:56 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

jadel wrote:
Wed Mar 06, 2019 10:22 am
tlfong01 wrote:
Wed Mar 06, 2019 12:58 am
Big Picture and Long Description Please! :mrgreen:
My question is more about a general possibility. Could I control let's say five electromagnets using one relay board and one power supply?
(while supplying each magnet with about 12V)

Big Picture and Long Description Please!
by jadel
Wed Mar 06, 2019 10:22 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

tlfong01 wrote:
Wed Mar 06, 2019 12:58 am

Big Picture and Long Description Please! :mrgreen:
My question is more about a general possibility. Could I control let's say five electromagnets using one relay board and one power supply?
(while supplying each magnet with about 12V)
by tlfong01
Wed Mar 06, 2019 7:07 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

Flyback diode for Songle 5V Relay Now I want to know the energy stored in the Songle 5V relay, then select a Schottky diode strong enough to swallow the flyback in one bite. Songle 5V Relay Inductance ~= 40mH ... Energy Stored in Songle ...
by tlfong01
Wed Mar 06, 2019 6:36 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

tlfong01 wrote:
Wed Mar 06, 2019 6:29 am
tlfong01 wrote:
Wed Mar 06, 2019 5:54 am
Flyback diode for Songle 5V Relay
Now I want to know the energy stored in the Songle 5V relay, then select a Schottky diode strong enough to swallow the flyback in one bite.
Songle 5V Relay Inductance ~= 40mH
...
by tlfong01
Wed Mar 06, 2019 6:29 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

tlfong01 wrote:
Wed Mar 06, 2019 5:54 am
Flyback diode for Songle 5V Relay
Now I want to know the energy stored in the Songle 5V relay, then select a Schottky diode strong enough to swallow the flyback in one bite.

Songle 5V Relay Inductance ~= 40mH
...
by tlfong01
Wed Mar 06, 2019 5:54 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

... J (not sure if the unit is Joule! :mrgreen: ) = 625 uJ ??? (not proofread, because I cannot count more than 5 zeros!) Flyback diode for Songle 5V Relay Now I want to know the energy stored in the Songle 5V relay, then select a Schottky diode strong enough to swallow the flyback in one bite. ...
by tlfong01
Tue Mar 05, 2019 1:10 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

I am 90% sure that you don't need any flyback diodes for the relays, because the relays are driven by ULN2803 octal darlingtons with built in flyback diodes. Just checking you mean I don't need it across the relay not the whole circuit, right? [/color] ...
by tlfong01
Mon Mar 04, 2019 6:18 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

I am 90% sure that you don't need any flyback diodes for the relays, because the relays are driven by ULN2803 octal darlingtons with built in flyback diodes. Just checking you mean I don't need it across the relay not the whole circuit, right? No flyback ...
by jadel
Sun Mar 03, 2019 4:36 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

pcmanbob wrote:
Sun Mar 03, 2019 3:58 pm

In reference to
Capture2.PNG
This diagram
Capture2.PNG (112.12 KiB) Viewed 2412 times
And this
tlfong01 wrote:
So there are at least three circuits you can choose.

(1) Small NPN BJT such as 2N2222 and 5V relay (Note 1),

by jadel
Sun Mar 03, 2019 3:41 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

1. I am 90% sure that you don't need any flyback diodes for the relays, because the relays are driven by ULN2803 octal darlingtons with built in flyback diodes. Just checking you mean I don't need it across the relay not the whole circuit, right? 2. The ...
by jadel
Sun Mar 03, 2019 10:20 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

If you don't have the link, you can show me a picture of you module, or skim the following posts and tell me which relay looks like yours. https://www.amazon.co.uk/gp/product/B07568JFNV/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 I only wanted to clarify that it was a board ...
by tlfong01
Sun Mar 03, 2019 1:53 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

Note - if you have already bought a 12V relay, you can use it, getting the same 12V power for electromagnet. This question might seem silly but I'm a bit confused by the phrasing. Does this mean I don't have to use an external power supply and ...
by jadel
Sat Mar 02, 2019 10:08 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

Note - if you have already bought a 12V relay, you can use it, getting the same 12V power for electromagnet. This question might seem silly but I'm a bit confused by the phrasing. Does this mean I don't have to use an external power supply and ...
by mahjongg
Sat Mar 02, 2019 3:26 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 11732

Re: Connecting electromagnet to pi

... this type of circuit work for it. https://forum.allaboutcircuits.com/proxy.php?image=http%3A%2F%2Fimg4.hostingpics.net%2Fpics%2F483312transistorrelaysolenoidvalveflyback.png&hash=ecb29a13ff8e50f6fb20e7c79773d9f3 Also from this circuit would I have to use both the GPIO pins and the relay ...

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