# Driving a pair of solenoids with a 555?

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#### EvilGenius

##### Member
I am not sure why I did not think of this earlier. If the solenoids are only on one at a time, and following Pommie's initiative, why not just use a 555 timer, connect it to a relay, and then use both poles of relay's outputs to turn each solenoid on/off at a time. N/O for one and N/C for the other.
The other idea is to just use a small PIC (microcontroller) with two pinouts for two NMOS circuits. This way the timing can be reset via a simple programming. Or use the thrid pin with a variable resistor to set the timer.
The third, simplest, and cheapest way is to hand OP a switch and a bulky alarm clock. "When the bell goes off, throw the switch".

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#### spec

##### Well-Known Member
Note: this is a joke circuit

How about a traditional cross coupled-multivibrator with the solenoids as the collector loads.

You could do the whole thing with a couple of Darlington transistors (TIP120C), two resistors and two capacitors (and a prayer).

spec

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#### EvilGenius

##### Member
How about a traditional cross coupled-multivibrator with the solenoids as the collector loads.

You could do the whole thing with a couple of Darlington transistors (TIP120C), two resistors and two capacitors (and a prayer).

spec
Funny I thought of the same thing this morning reminiscing my childhood lamp chaser circuit.
By the way Velleman has an inexpensive ($5.50), 555 adjustable timer board kit (MK111) that controls pulse and pause time via one relay. I tripped over the googling cord this morning. And yes I woke up on my funny bone. #### spec ##### Well-Known Member Most Helpful Member Funny I thought of the same thing this morning reminiscing my childhood lamp chaser circuit. By the way Velleman has an inexpensive ($5.50), 555 adjustable timer board kit (MK111) that controls pulse and pause time via one relay. I tripped over the googling cord this morning. And yes I woke up on my funny bone.
I have read many of your posts and have come to the conclusion that you have an inventive mind and a good sense of humor

spec

#### AnalogKid

##### Well-Known Member
How about a traditional cross coupled-multivibrator with the solenoids as the collector loads.
You could do the whole thing with a couple of Darlington transistors (TIP120C), two resistors and two capacitors (and a prayer).
Also thought of that, but - the circuit puts -12 V across the base-emitter junction, and most transistors don't like that. You can clamp it at -5.1 V with a zener, but now you have a forward-biased diode in parallel with the base-emitter junction, which will make the large timing capacitors larger with single transistors, and really mess up the circuit with darlingtons. Almost done with my sch.

ak

#### EvilGenius

##### Member
Here is my last thought on one 555 and one relay. The simulation might not be 100% accurate but you get the ideal.
The two relays on the right are the solenoids (don't have a good representation for them).
https://tinyurl.com/gopww8e

What is that clicking noise?
Wonder if that is what Abba used in their disco lights!

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#### spec

##### Well-Known Member
Also thought of that, but - the circuit puts -12 V across the base-emitter junction, and most transistors don't like that. You can clamp it at -5.1 V with a zener, but now you have a forward-biased diode in parallel with the base-emitter junction, which will make the large timing capacitors larger with single transistors, and really mess up the circuit with darlingtons. Almost done with my sch.

ak

Hi AK- it is a joke circuit- but dead simple.

spec

(PS- you will not catch me using a differentiating oscillator for real- they are a pet hate)

#### EvilGenius

##### Member
Hi AK- it is a joke circuit- but dead simple.

spec

(PS- you will not catch me using a differentiating oscillator for real- they are a pet hate)
Its too late. You already posted such a circuit. You can't take it back.

#### spec

##### Well-Known Member
Its too late. You already posted such a circuit. You can't take it back.
Ah, but take a look at the post now.

spec

#### EvilGenius

##### Member
Ah, but take a look at the post now.

spec
I did not post any of the above. I just came in this thread because someone said there is a nice buffet.
Thank you for earlier kind compliment sir. Did not want to leave it out there.

#### EvilGenius

##### Member
Joking aside once OP and you fine gentlemen decide on what design you are going with, draw a schematic and I will be glad to post an optimized PCB layout for it!

#### spec

##### Well-Known Member
Joking aside once OP and you fine gentlemen decide on what design you are going with, draw a schematic and I will be glad to post an optimized PCB layout for it!
Wow- that is a kind offer.

spec

PS: what ECAD do you use?

#### EvilGenius

##### Member
Wow- that is a kind offer.

spec

PS: what ECAD do you use?
I use Kicad. But if OP does not have a fancy software, I can post the layers in high quality pdf.

#### rfranzk

##### Member
Love the shop humor. I didn't even think about using a relay which would work just fine but I would like to do something solid state.
What is that clicking noise?

Really neat simulation by the way.

The alarm clock and manual switch might work. Maybe I could use a couple of reed switches with a magnet on the second hand? I enjoy reading a lot of the topics on this site but am not capable enough to chime in often.

But most home constructors do not like working with surface-mount.

I am in the process of constructing an arduino controlled toaster oven so I can do some surface mount projects.

I am just starting to learn Eagle by Cadsoft but a lot to learn and I am an old guy. Doesn't sink in like it used to. Life gets in the way too.

I am really impressed with everyone's willingness to help out with drawings, simulations, etc. Shows a passion for what you do. Thank You, Thank You,
Thank You.

Spec. I am leaning toward using your circuit as its pretty simple and fits the requirements. Robust enough to use on higher current demands if needed. Could you add a couple of led's to indicate when the solenoids are powered on?

oking aside once OP and you fine gentlemen decide on what design you are going with, draw a schematic and I will be glad to post an optimized PCB layout for it!

That would be awesome!! Give me a chance to get some more experience in etching boards as I have done very few.

AK's suggestion of using a digital period generator would provide a Rolls Royce plus performance but with more cost and complexity.

Maybe a next project.

Thanks everyone for all the help.

#### spec

##### Well-Known Member
Hi RF

I am just starting to learn Eagle by Cadsoft but a lot to learn and I am an old guy. Doesn't sink in like it used to. Life gets in the way too.
I was in the same boat as you about 18 months ago. If you have got over the initial hurdle of actually getting a component from the library on to your schematic ('Use' command), you will find EAGLE a nice friendly ECAD.
Spec. I am leaning toward using your circuit as its pretty simple and fits the requirements. Robust enough to use on higher current demands if needed.
A good move I would suggest. It is a pretty standard configuration and provides good flexibility is terms of devices that can be driven and at high speed too if necessary.
Could you add a couple of led's to indicate when the solenoids are powered on?
Think I can manage that.
Thanks everyone for all the help.
No probs from me.

spec

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#### EvilGenius

##### Member
That would be awesome!! Give me a chance to get some more experience in etching boards as I have done very few.
I can send you the pdf so that you don't have to recreate it in Eagle. You can do that later.
We can help you with tips on a home brew board. I am hoping you are using the laser printer method and not the hand drawn method.
Spec can hand draw the led's on his design and pass it on.

#### EvilGenius

##### Member
Spec
Is the pinout of 555 correct in this digram? Looks like pin7 and pin3 are swapped. Also no resistor between pin7 and 8 intentional?

#### spec

##### Well-Known Member
POST ISSUE 8 of 2017_01_22

Hi again RF,

Below is the latest schematic for the solenoid driver which includes LEDs to indicate when the solenoids are energized.

The LED forward current is set to around 10mA by the 1K resistors which can be changed to alter the LED brightness that you want. The working formula for choosing the resistor value is 10V/R = LED If.

ERRATA
(1) Change N2 to TC4428A
(2) Change C1 to metal film type, Kemet #: R60DR5470D50K
(3) Q2 should read IRF520

NOTES
(1) If the potentiometer is to be mounted remotely on long leads, as RF has indicated, the two signal leads must be twisted in a screened cable. The screen must be connected to the timer chip power supply OV line as close as possible to the timer chip Ov supply pin.

DATASHEETS
(3) https://www.vishay.com/docs/91017/91017.pdf
(4) https://www.kemet.com/Lists/ProductCatalog/Attachments/110/KEM_F3103_R60.pdf
(5) https://www.digikey.co.uk/product-detail/en/kemet/C1210C226K3RAC7800/399-11958-1-ND/5267671

SUPPLIERS
(1) C1 (47uF): https://www.digikey.co.uk/product-detail/en/kemet/R60DR54705050K/399-12459-ND/5730950
(2) C2 22uF, 25V, X7R, +-10% ceramic capacitor: https://www.digikey.co.uk/product-detail/en/kemet/C1210C226K3RAC7800/399-11958-1-ND/5267671

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#### Pommie

##### Well-Known Member
Personally, the way I would do the output would be the good old fashioned way. Something like,

Base resistors around 470R LED resistors to suit (800R or there abouts).

Mike.
Edit, just checked data sheet and to get BD139 into saturation needs 50mA so if problematic change base resistors to 270R.

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#### spec

##### Well-Known Member
Spec
Is the pinout of 555 correct in this digram? Looks like pin7 and pin3 are swapped. Also no resistor between pin7 and 8 intentional?
Hi EG,

No that pin arrangement is intended.

Discharge gives a nice fast clean drive for the gate driver chip and the CMOS 555 Q output swings rail to rail so it generates accurate timing.

Good observation though.

spec

PS latest schematic at post #38

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