Calculate how many amps a solenoid needs

[The Master]

Hi. I need to make a circuit to control some solenoids. What i would like to know is how to calculate how many amps each solenoid needs so i can get the components to match.

I know the Voltage, wire thickness and number of turns on each coil. Do i need to know anything else and is there some kind of formula for working it out?

[chuck]

you can use ohms law

What is the voltage and the resistance of the coil you then can work out the current draw

The soleniods that we use have 3 wires one is ground, the other is holding voltage and th last one is the pull in voltage, So you put power to the pull in (this pulls the soleniod in) and then the holding volatge takes over, then the power is removed from the pull in. The ones we use can draw up to 30amps only if hold the holding voltage is powered up first.

What type of solenois are the ones you are using ?

[The Master]

The solenoids are for a pinball machine. I looked up ohms law on the internet because i havnt used it since school. I think i worked everything out correctly and it appears that these solenoids are using 0.02 amps each at 55 volts.

Most of them are just 2 terminals but 2 of them (for the flippers) have the firing coil and the holding coil. There shouldnt be more than about 12 solenoids and the rectifier i want to use is rated at 8A. As long as ive calculated it correctly that should be fine. 0.02A does seem a little small for a solenoid though

[T.Jackson]

The solenoids are for a pinball machine.


Repairing or making a pinny?

I used to have some nice pinball machines back in the good'ol days when I actually had a dollar to my name.

High Speed by Williams 1986
Getaway, Williams 1992
Shark, Hankin 1981
Space Station, Williams 1987
Street Fighter II, Gotlieb 1993
Fish Tales, Williams 1992

Plus a couple of other Bally ones, late 70's, so long ago I've forgotten. Space Station was unreal.

Not easy to repair! (Lost a lot of hair)

[T.Jackson]

Arguably one of the most mechanically complex pinball machines ever made was "Haunted House", by Gottlieb 1982. http://www.youtube.com/watch?v=P5UCvb3FwnA

[The Master]

They used to have fish tales at a pub i used to go to. Then they switched to dodge viper which was also a good game.

The most complex one ive seen so far is the star trek one. There are just so many moving parts and about 4 different ways for the ball to go under the table and pop out somewhere else.

Im actually making my own game from scratch. Ive been playing pinball for so many years and always loved electronics so i thought it would be nice to make one. Ive made about 4 rough versions so far so now ive got some really expensive wood for the playfield and just about all the tools i need. I think im just a spot welder and vaccum former away from starting.

Most of the parts were from an old playfield. My local coin-op repair shop had a harley davidson that was beyond repair so they gave me the playfield for nothing with almost all the parts still attached. A few visits to Ebay and pinballheaven later and ive got everything i need.

Im making the circuits myself (thats half the fun) and thats where this thread comes in. Ive been testing my circuit using a 10A rectifier but its one of those that has spade connections. The only one i can find that can fit directly to a PCB is 8A. I need to figure out how much current will be drawn so i know if it will work. If not then i can either use 2 rectifiers or put some kind of limit on how many solenoids can fire at a time.

This might sound like a stupid question but how do you measure resistance with a multimeter? I used to have one that was easy to use but this new one ive got is so confusing. It only has settings like 200ohms, 2K, 200K.

[chuck]

you can put it on either of those settings if it's more then 200 ohms your meter will display OL if it's more than 200ohms

There is a better way of doing it, use your meter to read amps then put it in line of the soleniod and power it up and this will give you your amp reading.
Not sure what meter you have got but the black lead stays where it si and move the red lead into the ohter socket (it should say 10a), then connect red lead to the power supply the black lead to postive feed of th soleniod then the ground to ground and turn on power

then you can use your readings to work out total say if they are 55V then lets say if it draws .200 which is 200ma times that by 8 which give 1600ma (1.6A) which means you will only need 1 8amp recicitfer

[The Master]

Ahh. Yes, there is a seperate socket for 10A (no wonder it wasnt working).

Why do you times by 8?

Just to get things straight. When my multimeter is set to 10A does that just mean i cant put more than 10A through it or do i have to times/divide the result by 10? Same for the ohms. If i set it to 200ohms then will 10ohms display as 10 on the display or would it be 2000 or 0.05 or something?

[chuck]

No it will display what ever is been drawn, so no you don't times/divide the reading. so if it draws less than 1 amp the meter will display .200 say or anything over 1 amp it will dispaly 1.5 say. The same goes for the resistance reading only if your set to 2K the and put say 200ohm on there is will read 0.200 and if to put 1K on the it should read 0.999 tp 1.100K

I only times it by 8 to show you, All you need to do is times the reading by the number of solenoids you are running, so if you got 4 then times it by 4, It would pay for you to allow and extra .5 to 1Amp say for all the stuff you will have runnig of the rectifier

[The Master]

Thanx. That really clears a few things up. My new multimeter is pretty confusing at first glance and i was never shown how to use one properly in school :@

I just wondered where 8 came from. Im not sure about the total amount exactly yet but all that has to be arranged before designing the circuit anyway.

Yes, allowing a little extra is always a good idea. Im going to work it out asif all the solenoids are on at the same time. Realisticly i dont think that could ever happen but if a PIC chip goes wrong somewhere and turns them all on i dont want it to start smoking.

Just one more small question about the settings. When moving from 200ohms to 2K the decimal point moves. Is this just so the smaller numbers can be measured with greater precision?.

I have to remember that its measured in Kohms too. 1 = 1K and not 1ohm

[The Master]

Something else ive just thought of. Since im using an AC PSU and a rectifier i need a capacitor. Most of the solenoids are fine but the flipper solenoids buzz a bit because of DC ripple. In this case (or for any other circuit) how do i know what capacitor to use? Ive been told that 24uf is enough but i dont know where that figure came from. Is there a name for this type of equation?

[chuck]

it just means that you can measure higher values that's all, for your meter
Has for the cap the normal rule of thumb is 1000uF per amp, I think you would find that a 24uF would not last long. or it would not remove any ripple out of it at all

[The Master]

Thats what i thought. It seemed a really small value for solenoids. "1000uF per amp" thats easy to remember thanx!

[T.Jackson]

Im actually making my own game from scratch.


This guy here http://jamiesgarage.com/ has started one from scratch. Looks like a bloody eyesore, think he's only doing it to strike up keywords with google and make money from ads. I believe it usually takes a team of around 20 to 30 people to develop your average machine, not to mention a couple of million dollars at bay. Too ambitious for me.

One of the most sought after pinball machines is "Medieval Madness" http://www.pinball.com/Williams/games/medieval/

If you ever come across one on the cheap that needs a bit of tlc (or even a full rebuild) then I suggest grabbing it. You usually don't get much change from 10 grand from one in the mint. Rumor has it that, it's almost impossible to get a man to part with one.

[The Master]

Im fully aware of how hard it is but i really do like a challenge and with the amount of stuff involved its been great for learning new things.

I did do a lot of reasearch about pinball machines back when i was at school. My GCSE project was my first proper pinball machine although it was a bit of a basic one. I did see that there were a lot of people spending years designing and making them but ive done projects that big before.

I got a lot of the parts given to me and ive been on ebay for a few too so i have just about everything i need now.

Mine wont look so bad. My GCSE pinball did look a bit crap because i only had spray paint to paint it with. Now i know someone in america who has some kind of big printer and he can put all the images onto something like vinyl so i can stick them onto the wood. Its not as bad as it sounds. It should look really profesional when its done. He has made some good signs for companies in the past.

I seem to like very ambitious projects. You only have to look on these forums for my threads around halloween to see that :P

Ive not seen any pinball machines that i could get cheap and do up. They are either way past repair or i cant get them. I like the idea of making my own from scratch though. Its not just replacing a few parts its the whole design bit too. I can do all the things that some machines should have done.

Believe it or not the theme is actually horror. Mix that in with hardcore dance music (or maybe dutch gabber) and it should be a fun game to play. There will be some mini Martin MX1's (http://www.martin.com/product/product.asp?product=mx-1) around the playfield too. Im not sure if they will change color yet. Definately not change pattern but they will have moving mirrors. There will be a lazer light and some mini strobes too (im thinking about using camera flashes for them). Im still looking for the ideal UV lights too. I think UV cold cathode lights should work fine.

I aim to beat pinball 2000 too. They have something like 6 simple connectors on the playfield to link to the backbox. My aim is to have only 2 connectors with less than 10 wires between them.

Im not sure how long its goin to take. Im having trouble finding time to do anything with it at the moment. Once i start building it i think it should only take a few months. Routing out the playfield will take longer than anything because ive just got a normal router (not a CNC type thing)

[T.Jackson]

Mine wont look so bad. My GCSE pinball did look a bit crap because i only had spray paint to paint it with. Ive not seen any pinball machines that i could get cheap and do up.


All pinball machines that I know of have the cabinets spray painted and the artwork airbrushed. $2,000 can get you something half decent from the early 90's -- if you look hard enough. Stay clear of Street Fighter II, terrible machine, possibly one of the worst Gottliebs around, hard-to-sell even at $1,500. High Speed is an excellent machine on the cheap, in fact most William's pinballs are brilliant. $1,000 might get you a mid to late 80's one that's a bit rough around the edges.

Best of luck with the project!

[The Master]

All pinball machines that I know of have the cabinets spray painted and the artwork airbrushed.


Im not sure but some that ive seen have something stuck on them. Its not the type of thing i was going for but it wasnt paint. The vinyl should give it a nice finish too.

The person doing the vinyl says he can make the front of it sticky so thats the decals sorted to

The playfield im definately going with vinyl for. I know someone who is really good with photoshop so i can give him the design of the playfield and he can put the images in. The harley davidson playfield i have seems to have a vinyl cover then its either varnished or laminated in some way.


Best of luck with the project!
Thanx. It should be fun :)

[T.Jackson]

Playboy by Bally 1978, so so rare in this condition. THE most collectible pinball of the 70's. http://cgi.ebay.com.au/BALLY-1978-PLAYBOY-PINBALL_W0QQitemZ290218943538QQihZ019QQcategoryZ39 45QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I could have bought this machine bout 15 years back for $500. I'm kicking myself for not.

[T.Jackson]

Example of a "mediocre" early 90's machine going cheap. Cue Ball Wizard -- not as brilliant as Fish Tales but certainly not quite as terrible as Street Fighter II.
http://cgi.ebay.com.au/Gottlieb-Cue-Ball-Wizard-Pinball-Machine_W0QQitemZ150229023018QQihZ005QQcategoryZ39 45QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[The Master]

I saw one of those the last time i was in america. I think it was in TGI Fridays (if thats the right name) on I-drive (florida). It looked in pretty good condition too.

I hate seeing pinballs that havnt been looked after. They had an addams family one at my local club but half the things dont work. The rubbers arnt rubbery anymore. The electric chair is inside the hole under where it should be and the ball keeps getting stuck on everything.

It annoys me because if something breaks most places will give you your money back and turn the machine off. Then they turn it back on the next day asif it would magically fix itself.

By the way. Do you know if a TFT or LCD exists thats about the size of a pinball's dot matrix? Im having a 17" TFT in the backbox in the middle but it would be nice to have one in place of the dot matrix too. I was reading some threads on here the other day about using a screen (from a mobile phone i think) and displaying things on it. I want to buy a new phone soon so maybe a little screen on the playfield would look good

[T.Jackson]

It annoys me because if something breaks most places will give you your money back and turn the machine off. Then they turn it back on the next day as if it would magically fix itself.


Oh there's some seriously shady characters in the amusement industry (what's left of it that is)
They range from con artists to pedophiles, assassins and mobsters so I believe.