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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: 2665

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 9:35 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 2665

Re: I2C I/O PORT EXPANDER QUESTION

How much time would you spend on your I2C I/O PORT Expander Project Your project of using Rpi to drive 260 devices using an IO expander is a very complex project, for sure not for the faint of heart newbies. I already have 5 years hobbyist experience in Arudino and another 5 hobbyists years experie...
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: 2665

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 8:02 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 2665

Re: I2C I/O PORT EXPANDER QUESTION

tlfong01 wrote:
Fri Mar 08, 2019 6:35 am

ULN2803A Datasheet Summary

Now I am reading the datasheet and making a summary.
...
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: 2665

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: 2665

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 2:55 pm
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 2665

Re: I2C I/O PORT EXPANDER QUESTION

1. I have a keypad . 2. could be a RELAY, or ACTUATOR. 3. 260 signals 4. can't be too apart as it should fit in a case . How deep is your case? 1. But nobody is using any keypad now. Everybody is smart phone touch pad. 4. Now I have fitted 4 relays on 10cm x 15cm prototyping board. I guess with the...
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: 2665

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 5V. MCP23017 + ULN2803 Relay Circuit [/...
by tlfong01
Thu Mar 07, 2019 7:23 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

50Ω 17mH[/b][/color] Electromagnetic Buzzer Testing 6Ω DC3V~6V TT Motor Induceance Measurement - Unsatisfactory I found the inductance of the motor roughly 2mH. Perhaps because the coil resistance is too small, so the measurement is difficult to make. I found Vr even leading Vs. I guess there is so...
by tlfong01
Wed Mar 06, 2019 3:00 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

tlfong01 wrote:
Wed Mar 06, 2019 2:04 pm

50Ω 17mH Electromagnetic Buzzer Testing

Electromagnetic Buzzer Testing
https://youtu.be/EFLLeVPuYbs (youtube)
...
by tlfong01
Wed Mar 06, 2019 2:33 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

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: 3967

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: 3967

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 tlfong01
Wed Mar 06, 2019 7:40 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 2665

Re: I2C I/O PORT EXPANDER QUESTION

Do you know many PCA9685 does raespberry support? The looks easier with this chip because of its libraries. PCA9865 Not Strong Enough to Drive Relay I forgot to point out two things: (1) PCA9865 is only TTL 25mA output only, not strong enough to control a 5V relay which needs 70mA. You may need str...
by tlfong01
Wed Mar 06, 2019 7:07 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

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 Relay = 100uJ Now I know the inductance of the Songle relay is...
by tlfong01
Wed Mar 06, 2019 6:36 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

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: 3967

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: 3967

Re: Connecting electromagnet to pi

the average inductance of the electromagnets is roughly 5mH. the average inductance of the solenoids is roughly 4mH. Finding Energy Stored in Solenoids Anyway, let me now trying to calculate the energy stored in the electromagnet ZYE1-P20/15 DC6V 0.5A. E = 1/2 * 5mH * 0.5A ^ 2 = 0.5 * 5 * 0.001 * 0...
by tlfong01
Wed Mar 06, 2019 1:21 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 2665

Re: I2C I/O PORT EXPANDER QUESTION

Do you know many PCA9685 does raespberry support? The looks easier with this chip because of its libraries. How many PCA9685s can Rpi talk to? You might have seen my old post showing a Rpi with 4 working TSX0104 based demux I2C and 4 SPI channels. In other words, I can manually (by jumper) or by py...
by tlfong01
Wed Mar 06, 2019 12:58 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

which the one? Big Picture and Long Description Please! :mrgreen: Oh my goodness, you speak like my girl friend - shorter than her mini skirt. I wish you speak like my grandma, longer than her wrinkles. :mrgreen: Big/Long Example https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=234552&sid=d7...
by tlfong01
Tue Mar 05, 2019 3:09 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

jadel wrote:
Tue Mar 05, 2019 2:42 pm
tlfong01 wrote:
Tue Mar 05, 2019 2:32 pm

All magnets can share the same power supply, if total power is not exceeded.
Would the circuits be similar to the one for a single magnet or would I have to make big adjustments?

which the one? :mrgreen:
by tlfong01
Tue Mar 05, 2019 2:57 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

the average inductance of the electromagnets is roughly 5mH. the average inductance of the solenoids is roughly 4mH. Finding Energy Stored in Solenoids Now that I have a rough idea of the order of the inductance of the electromagnets and solenoids I am playing with is around 3 to 5mH , I can now ca...
by tlfong01
Tue Mar 05, 2019 2:32 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

jadel wrote:
Tue Mar 05, 2019 2:29 pm
Thanks for the help everyone got it working.
Just curious if I wanna have more than one magnet does each need it's own power supply or could I use the same one for more than one magnet.
All magnets can share the same power supply, if total power is not exceeded.
by tlfong01
Tue Mar 05, 2019 2:23 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

My conclusion is that my results are not reliable and not repeatable. I can only said that the average inductance is very very roughly 5mH . Measuring Solenoid Inductance - Unsatisfactory Results I measured 4 solenoids, from 0.8N to 20N. The results is not satisfactory at all. Two solenoids find Vr...
by tlfong01
Tue Mar 05, 2019 12:59 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3967

Re: Connecting electromagnet to pi

I measured 1 to 4 magnets and found it very tiring to do the measurements, perhaps because (1) the magnet has a big range of values, so the values for 1, 2, 3, and 4 magnets do not add up proportionally, (2) My visual measurements are not accurate at all (I should have used the scope's digital rule...

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