# (HELP) 555 Timer that flickers on and off a 12V 2A linear solenoid electromagnet

Discussion in 'The Projects Forum' started by SageRamsammy, Jun 19, 2016.

1. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
hi, I am trying to make a 555 timer circuit that can flicker on and off my solenoid, (2 seconds on, 2 seconds off, repeating) but I barely have experience with electrical engineering. The whole purpose of this is to click a button. Can anyone give me a circuit diagram showing me how to set this up with a 555 timer and proper resistors? I tried using an LED flickering 555 timer circuit diagram I found, and it works when I use an LED, but when I plug my solenoid in, nothing happens. Help would be very much appreciated

2. ### bushrat Member

Nov 29, 2014
97
23
555 timer can power up an LED, but it does not have enough current to power up your solenoid.
For proper timing, just google "555 timer calculator"
As for driving your solenoid, you must use a transistor as a switch, like so:
(ignore pin numbers and resistor values in this pic)

3. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
what do you mean by "driving my solenoid"?

4. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
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*what I said above

5. ### Alec_t AAC Fanatic!

Sep 17, 2013
5,956
1,132
You will also need a reverse-biased diode across the solenoid coil, otherwise your TIP122 will be fried by the back-emf pulses generated each time the solenoid is switched off. The diode should be rated to handle the same current that the solenoid draws. What are the voltage/current/resistance specs of the solenoid? (Edit: just noticed the figures in the thread title).

Last edited: Jun 19, 2016
6. ### bushrat Member

Nov 29, 2014
97
23
...enough current to power it up.
555 timer can only provide 20-30 mA or current, you need 2A. the transistor you use must handle so much power, as regular transistor will go "poof" or just melt.

7. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
12V
5.6 Ohm resistance

8. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
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do you have any videos or instructions for this? Sorry I really don't know anything about circuits, I'm just trying to build this project haha.

9. ### dl324 Distinguished Member

Mar 30, 2015
3,375
651
What is the full part number of the 555 timer you're using?

The bipolar version (NE555, LM555, and similar) can sink or source 200mA. CMOS variants will have much lower drive capability.

What is the coil resistance of the solenoid? A part number would be helpful.

EDIT: Just saw the posts giving solenoid particulars. Regardless of the timer you're using, you require a transistor to drive the solenoid coil. Like the circuit in post #2.

10. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
Is there a way to create the circuit I'm looking for without a 555 timer?

11. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
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OK new plan. If anyone can draw me a circuit diagram with proper labeling of the resistors/capacitors/ect (by using a key) that can power my solenoid on for 2 seconds and off for 2 seconds infinately, I will PayPal you \$5. I uploaded pics of the solenoid with the specs

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12. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
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ps: I'm gonna have to build it first before I give the \$5 to see if it works

13. ### Alec_t AAC Fanatic!

Sep 17, 2013
5,956
1,132
Yes, but the 555-based circuit is probably the simplest and cheapest.
How accurate does the 2 sec interval need to be ?

14. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
not accurate at all haha. It's just an estimate time. All I need this solenoid to do is to push a keyboard button

15. ### dl324 Distinguished Member

Mar 30, 2015
3,375
651
The way I read the duty cycle equation, you'll need to play tricks with discharge path to get a 50% duty cycle

Or you could use a flip flop to divide the timer output frequency by 2 and be guaranteed a 50% duty cycle.

Keep your \$5. We're more interested in teaching you to understand how to do it yourself. If your set on parting with your money, don't insult us. I made \$75/hour plus bonuses and benefits before I retired.

16. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
thanks for the help, but honestly I don't know what any of those diagrams mean haha. Is there any simpler way to explain it?

17. ### bushrat Member

Nov 29, 2014
97
23

very close to 2 sec on / 2 sec off.
D1 can handle 3 A, and Q1 can handle 2 A. Use heatsink on Q1

\$20 and I will build it for you (you pay shipping and cost of parts). J/K, you can buy parts and assemble it your self..

18. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
beautiful. Couple questions tho bc I'm really nooby to this stuff. What is "Cf" "D2" and "Q1"?

19. ### bushrat Member

Nov 29, 2014
97
23
Cf - regular 10 nanofarad capacitor, D2 diode, buy this specific number, Q1, transistor that can handle 2A of current, buy this specific number.

20. ### SageRamsammy Thread Starter New Member

Jun 19, 2016
16
0
Sweet. And you mentioned "D1" but I see that nowhere on the diagram. By the way thanks for all this help, really means alot