lol, serious props on that, there’s a hack indeed.

ummm 18 volts is a little high (probably signs that the voltage regulator took a crap on you) :P

14.4v should be the output of a working car alternator/regulator. But if it works when you plug it in, and not magic smoke escapes… cool :P

Anything intended to work off of a car’s 12v line normally tends to have leeway in how much you can over volt it. Most go to 15v before stuff breaks, because most radios have internal voltage regulation circuits to divide voltage and stuff.

At least he “soddered” things together as opposed to the much worse “twist and tape” method.

This guy is asking for some crack head / meth addict to break into this car to steal that fancy pizza box computer he has laying on this back window deck. I would pay money to see the look the pawn shop broker would give this guy when he tried to sell this “computer” to them for another hit.
-g

My girlfriend’s car lacks a cd player, something like this might be just the ticket. It’s funny that it never occured to me; I’ve hacked together little stereos using an old PSU, CD-ROM, and a couple of speakers before (held together with duct tape, of course).

Hurm. I would say the voltage people are saying is way off. Ive done car stereos for years and rarely seen (un-intentionally) over 15 volts. They should put out 12 (from the batt) when off, and 14.4 when turned on. The cigarette lighter may drop some due to the low guage wire going to it. (and I wouldnt run more than a hundred watts or so through it w/o pulling another thicker wire). For the people saying that they are getting peaks of up to 50v, I disagree, youre having problems. If you do have voltages that high, fix your regulator before you fry everything in your car.
Anyway… Nice to see, Thought about doin something like this w/ an old dvd player years ago (before they were so common in cars)… sadly a CD player will run you about 30 bucks these days used.

I think the pics must have been taken with his 110 film camera/web cam hack.

The voltages people throw around refer to what you should be designing for, not anything one is likely to ever actually see in a car.

Yeah, if you have 50 VDC on the rail, something is wrong. But when designing with such things in mind, it would be nice if your product were to survive it. It doesn’t have to operate well under such conditions, but not burning up is good.

I think most everyone has missed the point of this hack… The idea was to build a stereo that cost absolutely nothing to make. This never claimed to be an alternative to your 2400 watt sound system. I was only intended to be better than what I had, wich was nothing…If you can do it better, then please, by all means, tell me how…

Ill tell you how,
wire it into the damn car’s battery intead of a retarded ass third grade wire running from the back of the car to the cigarette lighter.

All that creative inginuity just goes totally to shit when you are too inept to pull up a little carpet, some moldings and hook up a simple fusible wire to the cars battery. That way you wouldnt have to worry about any fluxuations from the lighter socket, and you still could use it for your cell phone, ipod, lighter etc. Any stereo guy would tell you that. if your goin to go through all that other trouble, why not take a little effort to do it right.

hehe blaine — have you actually ever put a meter to a car battery while charging? Or any battery charging at a voltage higher than surface voltage?

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As for why not just make an amp? Well, why make one when you have one already? Making a new one just seems a little over complicated when all you have to do is use one already built with features you don’t have to build yourself. That is why the site is called hackaday, not buildaday :P

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50volts! I measured 1337 jigawatts! Yeah, I agree with #12 – if you get that high a spike, fix your regulator. I don’t understand why it is thought that the regulators don’t do a good job at their one job(regulating :P) – most car ECUs don’t like sensors that don’t have a good ground, having voltage fluctuations like the ones being described cause quite a bit of problems o.0

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Last but not least “no money at the moment I decided to make this temporary car amp..” Is it the best hack we’ve seen? No. Is it a decent hack that fits his needs? Absolutely. And because it works with whatever voltage the car is throwing at it, props to jvc…

@ silver
actually, in a vehicle application, twist and crimp tends to be the best option. soldering can create little solder balls that can and do break off with all the bouncing around, causing problems down the road (pardon the pun). twist and crimp (while not as pretty as soldering, but decidedly better looking and longer lasting than twist and tape) is more durable.

Nice project. Reminds me of, was it 1985? All the radios were disappearing from cars in my parents’ town. Preferring bad sound over no sound, my dad took a really really cheapo old car radio. It didn’t even fit into the dashboard, so he timbered some sort of case for it. You know, a 27-drilled-holes-for-the-speaker type of case.

However he made the mistake of nicely painting the wood – so some poor idiot still stole it.

ohh yeah.. and the whole discussion about the Voltage Regulator: Put a cap (or a few) on both sides of the VR to keep the 5 volts constant, and whoever recommended the heat sync is right. With that VR, 12v in drops a lot of excess voltage as heat. 6 to 7 volts going in stays pretty cold. Even a strip metal works great.

#26,-”but it is STILL AC.”
I’m going to have to say a car produces dc, not ac, so yes it would have mattered… You can’t just switch the polarity and expect it to work…

chris, hacks like this are indeed worthy of hackaday and yours was no different: You revived a besieged bit of wayward electronics — that is quite a bit more than most can say. You did so in a way that not only stretched the original functions of the device, but also added to its capabilities. That’s good by my book.

Chris: To help you visualize the power situation.. look here http://www.allaboutcircuits.com/vol_3/chpt_3/4.html
and read up on the full wave (its the diamond shaped one) When AC goes in, DC of a particular polarity ALWAYS comes out.. that is important in your case because AC phase shifts back and forth, yet you always have DC polarity on the other end. Thus, with DC (from the car) going in, its the same as ONE phase of AC.. and it doesnt matter which phase. One phase has two diodes always working and two never working.. get it the other way and the working and non working diodes just change places.

For those of you that think the voltage in your car never gets to 50V, consider this.

If you behave, and your car is reasonably new, it probably doesn’t.

But the voltage can go really high if someone decides to disconnect the battery while the engine is running (google “load dump.”)

Jump starting and possibly battery chargers can also cause big spikes.

And if the ground straps between the engine and the car body get loose, this can also cause huge spikes.

There is a good reason that most quality automotive electronics are designed to withstand over 40V.

But, for the purpose of this hack, it doesn’t much matter. He never intended it to resemble “quality automotive electronics.”

OrbnLgnd… what the hell are you talking about? there’s not AC being used in this project at all. 12VDC from the vehicle’s electrical system, and then 5VDC going to the CD-ROM drive through the 7805.

Unless I’m missing something?

My bad for telling the kid he did something the right way (even if he didn’t understand why yet).

Forget all about AC. Look at the link I gave. Go half way down to the part that says “Full wave Rectifier circuit (bridge design). Forget about the arrows on the drawing.

Look at the Supply on the left (circle with a wave in it). Normally this is AC, but ASSUME that it is the car’s power supply (DC). Now, the first drawing with arrows on it shows what happens when the battery has the positive lead going into the top of the bridge. Notice the positive voltage goes through the diode on the right and comes out at the Positive pin of the bridge. The Black diodes are the active ones in this case (allowing voltage to pass), and the gray are inactive (blocking voltage from passing through).

The Next drawing shows what happens when the battery has the positive on the bottom. Notice that the positive voltage would go up from the bottom through the right diode and end up at the same place.

Positve will ALWAYS come out the right side of the bridge, and negative on the left, no matter which direction the battery is attached to the top and bottom.

If that doesn’t clear it up for everyone, I give up ;)
(I DO admit perhaps my first couple posts on the subject might not have been all that clear.)

#38: I see what you are saying. I’m not qualified in electronics, but I do understand a few things aout it I’m thinking 50VDC would be more typical in 24VDC or higher systems than in a 12VDC system. Semi trucks and some boats commonly use 24V+ systems, and some electrical equipment runs off of that.

My guess on the why is due to the sudden change in load, the regulator increases the voltage in an attempt to maintain the balance until it cuts off, thus creating a surge. Dunno.

“My guess on the why is due to the sudden change in load, the regulator increases the voltage in an attempt to maintain the balance until it cuts off, thus creating a surge.”

Kind of. An alternator and regulator do not regulate voltage in the same way as normal integrated circuit regulators, such as the 7805 in this project. The way an alternator works is that the regulator changes the current through the field coils to change the amount of magnetism produced by those coils such that the armature generates the necessary voltage no matter what the engine speed or electrical load is. In an ideal world that is.

But what actually happens is that those field coils have a lot of inductance. Inductance resists changes in current flow. Therefore you can’t change the field current instantly when a big load, such as the battery, is disconnected. There is a fraction of a second where even after the regulator has tried to reduce the current flow to the field coils the actual current doesn’t drop much. Durning this period you have way more field current than you need, so the voltage generated by the alternator shoots way up from where it is supposed to be.

If sufficiently heatsunk, is a 7805 regulator all that is necessary to produce fairly clean and stable 5V from a car cigarette lighter socket? Or do you need all kinds of extra fancy capacitors and zener diodes and stuff?

I built a car power supply with basically just a fuse, 7805, heatsink and fan, for a GPS and iPaq, but now I’m slightly worried that I might be giving them a really nasty feed. Don’t have a storage scope unfortunately to look at the waveform. Any advice or rules of thumb?

Oh, the car is kind of crappy and old so it’s safe to assume there’s little or nothing in the way of onboard smoothing for cigarette lighter accessories.

Now, after posting that, I see that I was replying to Chris Rybitski, the writer of this hack.

Before I noticed that, I assumed you were talking about a commercial car stereo, not the system in this hack. Real commercial car stereos are designed to take voltage spikes in the 40 volt range.

Your hacked up system isn’t designed to do that, but sometimes you might get away with it for a long time. Protection circuits aren’t needed until something goes wrong.

So don’t be surprised if it quits working someday after you jumpstart someone’s car or a battery cable comes loose.

But don’t worry about it either. This is a system you hacked together out of free parts. It’s OK if it isn’t designed perfectly. :) And even if it does break, you learned something in the process, and you’ll have an excuse to do it over again and fix the things you’ve learned how to do better the second time around.

I love it! Funny, and great work!

I have to agree that this isn’t pretty or simple, but hacks are somethimes neither.
I salute the effort!

If it works, it’s good! :D

This is truley a DIY, salvage operation to the fullest. Quintessential to the DIY philosophy. All you worried about aesthetics should take a course like ‘Radness 101′ because that’s exactly what you are not, rad.

Big ups. Salvage the Planet!!!!

PS. You’ve created such a disturbence within the hack a day community that you are now the fourth ‘most commented on’ project. Mad probs.

this project cracked me up :D the pictures of the case in the car and the close ups of the hacked up rear ‘panel’ just put it over the top – keep on makin things chad!

Don’t have a job per se, instead I started making random crafty things and selling them… easy work and easy money… Although I have the money to buy a car stereo I’m not inclined to becasue this system works just fine…