Switching From Batts to 11OV without Shutting down?

[crazybillybob]

I'm looking at Using a VOOM Pc (made for your car) In my Currrent Mod (R2Server) Here's a Pic of the VOOM
http://www.fccmonline.com/LanImages/R2/voomPC.jpg

I want to run it on an Internal 12V Batt when I'm driveing R2 Around, But when I park him I want to hook up 110VAC to him, so that I can Recharge the Batts and Run the PC For Long periods of Time (LAN PArties!).

I know I can get a 110VAC to 12VDC Power Pack. What I don't know is what kind of Curcuit I'm going to need to use to:
1, Enable power from power pack to Run the PC
2, Disable 12V Batt power (so the charging curcuit can charge it up)
3, Do all the Above with out the pc shutting down (or blowning up!)

So, I think this is kinda what I need but not sure how to do it



http://www.fccmonline.com/LanImages/R2/MagicCurc.jpg


I Can built just about any circuit if I have a Drawing, So building one is not an issue. But I'll also look at buying one if someone knows what I need to look For.

Thanks,
CrazyBillybob

[pointedsirforky]

Think I've got an idea for you.

http://caddish.ath.cx/TBCS/battery-ac-charger.gif

Two relays and a big assed capacitor should do the job.

relay 1 is a single pole, double throw type (one a or b switch)
this relay controls the power-source for the system

relay 2 is a double pole single throw (two on or off switches)
this relay controls the charging circuit, making sure its disconnected and not drawing power when on battery power.

Both relays should be rated for 12 volts input, and be rated high enough to handle the system's current.

the capacitor should be fairly large to avoid any power disruption when the system switches from battery power to ac power.

Hope this helps.

[Bum]

I'm no circuit designer but I'm thinking some diodes would be in order to dictate the flow.

[Xato]

Why not just use a UPS (uninteruptable power supply), they use a rechargeable electric battery, and when your computer is stationary, you can plug the power in through the UPS. UPS systems allow for continual flow of electricity while switching power supplies along with a whole other buttload of useful features.
Problem is, i think they're hella expensive.

[crazybillybob]

Xato,

That is an Idea...But I didn't want to go that way because of the following reasons.

1: the pc runs on 12VDC UPS's output 110VAC (the Inverter and extra parts are unneeded in this app)
2: HEAT!!!!
3: A UPS that would run as long as the 12V7Ah battery would weigh more then R2 does.
4: A Good one isn't Cheap
5: when you unplug them they all have this annoying Beep, Beep, beep that can only be stopped if you hit a button on the unit.......BEEP, BEEP, BEEP, Look out R2 going to explode!!! :eek: Not a comment I want to hear!



I was looking @ This if I put a normal Desktop PC in him, and is part of the reason the VOOM PC appealed to me!


Crazybillybob

[crenn]

You could always have a cheap 200W PSU suppling the 12v rail while the battery is charging......
I'm not sure how you design a circuit to detect when the PSU is turn on......I'll sleep on it and talk to you tomorrow. You would need at least a relay or 2........ and the PSU to have a 5v standby rail......

[GregoryJ]

Why dont you scratch the VoomPc and build a standard mini-ITX system. This way you can use all standard pc gear and the UPS system mentioned. That way it would reduce the possibility of R2 turning into a flamethrower. But... if you do want to go with a conversion a good place to start looking for the electrical components would be a place like PartsExpress.com. They may have some of the random electrical stuff you may need. 8)

[crenn]

Bob already stated why he wasn't going to use a UPS system. Also (depending on what UPS you get) a UPS plus normal computer components equals poor battery life. The voom PC is designed to be for cars, but you could build a much better system using a P4m mini-itx board. They only require 90W which isn't too bad..... but it would have better processing power....

[crazybillybob]

The Via MII1000 With the Setup I'm looking at should only use about 65W of power. The UPS's power to weight Ratio is too high. R2 without any extra stuff (just motors, batts, and Radio gear) will weigh 90+LBS.
An APC 1500 ups weighs in @ 37Lbs and has run time with a typical P4 Desktop of 15Mins. A 12V 7Ah batt weighs in @ less then 7Lbs and has a run time on the Voom of 2-3 hours. The bonus to using the Voom is that it is a compact, Robust, and can run on low power for a good length of time.

The relay Idea looks like it could work, I was thinking twin switches but the relays make mistakes much harder. I have a question in with the mini-box sales department asking if the power supply can handle minor drops in power (ie when switching power sources), but I have not heard back from them yet.

Thanks for the Ideas keep them coming.
Please keep in mind that putting a UPS into R2 is a last case thing... I'd much rather come up with a more elegant solution that is lighter (as Weight is the enemy !)


Crazybillybob

[Xato]

I'm just suggesting the UPS as the circuit, you can easily wire a different battery in. Plus the Beep noise can be easily fixed.
Most of the weight in UPS's is the battery they use... All the rest are the Needed components of the switchover and charge circuits. But enough on that... If you can find a good cicuit to make, i'd go with that, but a modded UPS is definately a backup solution.

Anyway, whats the power usage on the Vapochill? I can imagine it would be a lot. A good peltier element takes about 90w...
(I am thinking of the right mod right? lol)

[crazybillybob]

Xato,

the R2 mod your thinking of is the one made by "The Great Statan", his has the vapo-chill.

Mine is a 1:1 replica of R2 that Is R/c Controlled, that will bw used as a gaming server for LAn Parties.

R2 Server WorkLog (http://thebestcasescenario.com/forum/showthread.php?t=1092)
Thanks for the help!

Crazybillybob

[pointedsirforky]

And here I was thinking that my circuit design up there had addressed all possible problems. voltage drop, switching time drop all covered by the capacitor. the charger is automatically engaged once ac is plugged in..

I confused.

[snefan]

poor pointedsirforky :( lol

[crazybillybob]

Pointy,

Your Curcuit Is very nice. And will do just what you thought! I'm really looking at using it or a slightly modifed version of it. Gee...Go to a mod forum and someone goes and mod's your ideas! :D I'm looking over (in more detail) the specs for the ITX board and the power supply to see how much interuption it can handle. Either way I'll make sure I post what I come up with and tip my hat to those who helped come up with it! ;)

Thanks,
Crazybillybob

[GregoryJ]

you dont need a standard lead-acid battery... I put a small battery in my car to run video monitors and the audio system when the engine is off. It is a Recombiant gas discharge battery. It does not have (or need) water and is only about the size of a lawnmower battery and can be mounted in any position. here is a link to a similar one: http://www.lightningaudio.com/2004/products/product.asp?prodID=211

[crenn]

The problem with pointy's design is the fact that he hasn't thought about where the 12V to the DC-DC board is going to come from, which is why I mentioned the small 200W PSU to act as the convertor and to provide the 60W DC-DC board with a nice 12v line while the battery is charging. This then brings up the issue on how to get the 200W PSU to turn on. I could only think about one option. Hot wire the damn thing(which means it would be rendered useless unless you can put it back together again, btw, I'm talking about using it for a normal 20pin mobo) so that it turns on. This then brings up the issue of whether you want to press a button to make the PSU turn or do you want it to do it all by it self and then charge the battery as well. If you want it do it all by itself then you need some type of IC circuitry(I would recommend a PICAXE 18A, if you want something really simple and easy) and to wait 1-3 secs after the 5v standby rail turns on (to power the IC chip) and to then activate the PSU "switch", wait another second and then to deactivate the PSU switch(basically it will act as a virtual button). After this process has been complete it will then start to change some relays to connect the PSU to the DC-DC board giving it power, waiting about a second and then continuing to disconnect the battery from the DC-DC board and activating the charger and connecting it via more relays to the battery.

The only problem with this complex design that when you unplug the 110V lead, I'm not sure how quick the relays will change back to normal position. So you might need a button connected to the IC chip and when you press it, it reverses the cycle reconnecting the battery to the DC-DC board, ready for the unplug. The only problem is I would have no clue on how to design this circuit..... Pointy, you're good at those types of things, think you can design it?

[crazybillybob]

Crenn,
The 12V to power the PC when not on batts will be coming from a laptop type power pack (The Voom PC just needs 12Vdc to run) pointy didn't mention it because in the first post I didn't has about how to go from 110VAC to 12Vdc (I had that figured out...I thought) just how to switch from one voltage source to the other (at least that's what I thought I ask....may not have been real clear though).

Now on top of this I looked at the power boards DCV in range it can take up to 24Vdc....In talking with someone else they said why not hook it up like your car, the charger recharges the batts while providing power for the car. So I'm very much looking into that Idea as well. Plus the power board in this pc does all the startup delays (just configure some jumpers and it's ready to go) I am using a picaxe type micro controller in another place I shouldn't need one in the power supply (at least right now in the phase of design.....That could change at any time with out notice!)

Thanks very much for the Ideas and input. I would not have thought of them on my own!

Crazybillybob

[pointedsirforky]

Just to be clear, I had no intention of trolling for credit or such, I was just confused by questions that I thought I'd adressed.

S'all good. Lemme know if theres anything else I can do to help.