diy portable radio

[shanky887614]

ok long story short.

my makita radio broke and im not paying £100 for another when it only lasted a year (it was treated well and Hardly used)

anyway i found some info about people that had been making there own radios using an old car stereo.

it got me thinking, hmm a radio powered by 12v battery supply in a toolbox, after a bit of searching i realised a few people have used ammo boxes and posted guides.


after looking through a few for idea's i came across a drawing so i tweaked it a little bit.


what do you guys think of this?



im probably going to tweak it a little more because im going to run it off say 18650 cells instead of a drill battery (aa sized but 3ah cells)

below is the original drawing i borrowed




i just need to pick up a relay to swap between battery and mains

or i might get rid completly and just have it battery powered (will make it simpler)


what would be a good way to set a discharge limit? that is one of the things i am looking into at the moment

[smjcuk]

That was my hifi when i was a kid. I'd keep it simple and use a sealed lead acid battery in the toolbox with the head unit and just connect a trickle charger to it when you're not using it. Put a 10A fuse inline with the head unit and make sure you have the accessory supply wired up according to the radio instructions. The design above is totally overkill.

You can get some decent cheap head units that have USB ports these days as well so they make good stand alone mp3 players.

Assume you are in the UK, so hit gumtree.com for all the bits. You can probably do this for 50-60 quid easy.

[tron9000]

my makita radio broke and im not paying £100 for another when it only lasted a year (it was treated well and Hardly used)

I'd have expected more from Makita! But there it is, 1 years warranty: http://www.makitauk.com/service-care.html 

just a few things: remember to earth the metal box and I would keep the charge indicator, ditch the panel meter and somehow compliment another indicator with the charge indicator (e.g. bi-colour LED) to indicate when charge is low, and keep the 12V outlet.

OR instead of the 12V outlet, have a USB port with the power pins connected to a 5V supply, then you could charge your phone off it.

The panel meter seems a bit superfluous to your requirements for just a radio, when all you really need to know: is it charging? Does it have enough charge?

[shanky887614]

That was my hifi when i was a kid. I'd keep it simple and use a sealed lead acid battery in the toolbox with the head unit and just connect a trickle charger to it when you're not using it. Put a 10A fuse inline with the head unit and make sure you have the accessory supply wired up according to the radio instructions. The design above is totally overkill.

You can get some decent cheap head units that have USB ports these days as well so they make good stand alone mp3 players.

Assume you are in the UK, so hit gumtree.com for all the bits. You can probably do this for 50-60 quid easy.

to be honest the radio i picked up (a new sony) for £40 has a built in fuse (10amp) on the back so it doesnt need one.

thank you for the above post

my makita radio broke and im not paying £100 for another when it only lasted a year (it was treated well and Hardly used)

I'd have expected more from Makita! But there it is, 1 years warranty: http://www.makitauk.com/service-care.html 

just a few things: remember to earth the metal box and I would keep the charge indicator, ditch the panel meter and somehow compliment another indicator with the charge indicator (e.g. bi-colour LED) to indicate when charge is low, and keep the 12V outlet.

OR instead of the 12V outlet, have a USB port with the power pins connected to a 5V supply, then you could charge your phone off it.

The panel meter seems a bit superfluous to your requirements for just a radio, when all you really need to know: is it charging? Does it have enough charge?

the top picture is the rough design to what im going to use, the bottom one is the one i borrowed off someone else (i was going to use li-ion batteries to keep the weight down)

i might swap it to a couple fire alarm type batteries (sealed lead acid batteries) 12v 7a are quite small so will work well. plus i can use a car charger like you guys recommended

i was looking to get a good 8-10 hours out of it for use at work



in truth there is no charger in the uptodate plan.  i uploaded a copy that i was in the process of editing stuff out of

[tron9000]

i might swap it to a couple fire alarm type batteries (sealed lead acid batteries) 12v 7a are quite small so will work well. plus i can use a car charger like you guys recommended

erm, this was on my desk, are you meaning one of these (see attached)?

cos I can tell you, it ain't small and it weighs about a kilo!

[shanky887614]

i might swap it to a couple fire alarm type batteries (sealed lead acid batteries) 12v 7a are quite small so will work well. plus i can use a car charger like you guys recommended

erm, this was on my desk, are you meaning one of these (see attached)?

cos I can tell you, it ain't small and it weighs about a kilo!

sorry your right, i was thinking of the 2ah for the physical size



1kg is fine for weight and i would rather go for a larger battery.

that was one of the reasons i was toying with 18650 cells.  there aa size and are 3.7v and 3ah each.

the problem if i do go with the 18650 is i will need to look into putting a protection circuit or similar in

[tron9000]

18650 cells are not quite AA sized, but I know what you mean, they are similar but are not compatible, 18650's are bigger by about 25% in length and diameter.
http://en.wikipedia.org/wiki/List_of_battery_sizes#Cylindrical_lithium-ion_rechargeable
http://en.wikipedia.org/wiki/List_of_battery_sizes#Common_battery_sizes

I bought some a while ago off ebay for a head torch, and they were pants, utter crap, couldn't hold their charge! Plus the charge didn't cut out automatically, so had to keep an eye on it, was a bit paranoid about them over heating, leaking and consequently burning my shed down! Ironically, the ones I bought were called Ultrafire! Not a good choice of brand name for a Lithium based battery IMO!

 To get decent one's you will have to shop around, but be prepared to to pay a bit more than the ebay prices.

good thing about lead acid is they are easy to charge and are less prone to catching fire if they leak or get damaged.

[shanky887614]

18650 cells are not quite AA sized, but I know what you mean, they are similar but are not compatible, 18650's are bigger by about 25% in length and diameter.
http://en.wikipedia.org/wiki/List_of_battery_sizes#Cylindrical_lithium-ion_rechargeable
http://en.wikipedia.org/wiki/List_of_battery_sizes#Common_battery_sizes

I bought some a while ago off ebay for a head torch, and they were pants, utter crap, couldn't hold their charge! Plus the charge didn't cut out automatically, so had to keep an eye on it, was a bit paranoid about them over heating, leaking and consequently burning my shed down! Ironically, the ones I bought were called Ultrafire! Not a good choice of brand name for a Lithium based battery IMO!

 To get decent one's you will have to shop around, but be prepared to to pay a bit more than the ebay prices.

good thing about lead acid is they are easy to charge and are less prone to catching fire if they leak or get damaged.

you couldnt have picked a worst brand ill post a link

just one example

budgetlightforum.com/node/27603

to be honest i was going to go for the larger protected cells by say panasonic or sanya etc

[technix]

Here is what came to my head out front: single chip stereo FM receiver. Those chips are cheap, requires very few external components to work, and can be powered by a single 18650 cell for a very long time. Combine one of those with a TP4056-based Li-ion charger/protection chip and you get a working FM radio with internal rechargeable battery.

[tron9000]

you couldnt have picked a worst brand ill post a link

just one example

budgetlightforum.com/node/27603

to be honest i was going to go for the larger protected cells by say panasonic or sanya etc

well shheeeettt!
would'ya look at that! Bar-stewards!

[vk3yedotcom]

Great idea. If you can get a radio with a USB connection & MP3 player.  If you're into long distance AM reception you'll find the car radio works better than average.  As for the power source I used a split up 24v NiMH battery pack from old medical gear.  4 amp hours should be fine.  I use them for other things so the charger is external.  But if you've got room for an internal supply maybe put some terminals on it to make it a useful general purpose supply.  Or even a charger for cordless drills etc.

The acoustics of the box are really important for good sound quality.  I built one in an esky (basically 2 x plastic with air cavity).  Didn't bother with stereo - just used one speaker.  With the lid on (which makes a huge difference) the sound is fantastic.    Here's a video:

[shanky887614]

Great idea. If you can get a radio with a USB connection & MP3 player.  If you're into long distance AM reception you'll find the car radio works better than average.  As for the power source I used a split up 24v NiMH battery pack from old medical gear.  4 amp hours should be fine.  I use them for other things so the charger is external.  But if you've got room for an internal supply maybe put some terminals on it to make it a useful general purpose supply.  Or even a charger for cordless drills etc.

The acoustics of the box are really important for good sound quality.  I built one in an esky (basically 2 x plastic with air cavity).  Didn't bother with stereo - just used one speaker.  With the lid on (which makes a huge difference) the sound is fantastic.    Here's a video:

very nice, ill watch when i get home from work.

eventually its going to look similar to this



depending on the sound i might line it inside

[tron9000]

oooohhh, like!

Where can you get ammo boxes from? army surplus?

[shanky887614]

oooohhh, like!

Where can you get ammo boxes from? army surplus?

yes army surplus and ebay.   that is a 50cal Ammo box.

they have a waterproof gasket in the lid so very useful

forgot to mention you can get them on Amazon as well

[shanky887614]

ok ive had a rethink and this is my new plan (ill add the charger later and might put a 12v car socket in)



ive got the case in my car and some old speakers in the garage so as soon as i get the battery and some leads and crimps ill put it together

[shanky887614]

mod please delete duplicate

[BennVenn]

My girlfriend and I build this little guy up -

http://bennvenn.com/TDA7498.htm

More sound than you need and runs from Li-po packs which have low voltage protection and a charger. All in all, pretty cheap and good sound. Does bluetooth, USB, radio and has a remote.

[tron9000]

Does the stereo head have the relevant power management controllers already in it? also when plugged in and in use, is it ok to run off the trickle charger? Wouldn't you need a a separate supply when mains powered?

[smjcuk]

I'd use the trickle charger as the mains supply as well. Think of the battery as a huge capacitor in function when the charger is connected.

Technically this is the same as the alternator charging and providing power when your car engine is running and the battery providing power when the engine is stopped.

Schematic above is fine but the battery is a two port device so it makes sense to display it as one.

I'd also personally leave the charger and mains outside the unit for safety and so you don't have to carry it around.

[tron9000]

doesn't it depend on CC or CV trickle charging?

If it was me, I'd go for CV trickle charging and set the output of the charger to about 13V-ish and design it to supply 2A-3A max (shouldn't need much more, unless its a right boom box!), or have I just confused the 2 modes? (coffee still taking affect)

[smjcuk]

No idea to be honest. It was a "maintenance charger" akin to one of these: http://www.halfords.com/motoring-travel/bulbs-wiper-blades-batteries/car-battery-chargers/halfords-maintenance-charger - assume they are current limited based on the description.

I checked the battery voltage when connected and it was about 14.5v which wasn't enough to cause the head unit trouble.

[shanky887614]

surely most head units can take an input of 12-18v (maybe 24) just because of how common the battery size is

[tron9000]

to get more out of your battery, you want it to accept a wider input power, 10V or 11V to 18V.

EDIT: just re-read and I thought it should be clearer

[shanky887614]

hmm, ive just looked up the details of the battery i was going to use and its too big and heavy

2.5kg and it takes up a lot of space in there as well, i might have a look at stacking two smaller ones together or go back to the li-ion idea.

ill finish rough sketch in sketchup then decide

[BennVenn]

http://www.ebay.com.au/itm/DC-12V-6800mAh-Super-Rechargeable-Protable-Li-ion-Battery-With-EU-Plug-Adapter-/161534557672?pt=LH_DefaultDomain_15&hash=item259c35bde8

Grossly over rated, closer to 3Ah but has the under voltage protection and a charger. Over current kicks in at 2amps so maybe use two.