UD186413@NDSUVM1.BITNET (Space Studies Student Organization) (02/13/91)
I'm interested in building a converter that would allow me to run a
Commodore VIC 20 computer from a 12v motorcycle battery. The
computer needs a 9v ac input. Is it possible to synthisize this
easily? The current load is less then 3 amps max. The setup will
be used in a robot. Anyone have any ideas?
John Nordlie University of North Dakota
Space Studies Dept.cameronjames@snoc01.enet.dec.com (James Cameron) (02/13/91)
In article <91043.135514UD186413@NDSUVM1.BITNET>, UD186413@NDSUVM1.BITNET (Space Studies Student Organization) writes: >I'm interested in building a converter that would allow me to run a >Commodore VIC 20 computer from a 12v motorcycle battery. The >computer needs a 9v ac input. Is it possible to synthisize this >easily? For me this seems strange, since the computer's power supply will promptly convert the AC input back to DC. Why not open the box and provide the DC source after the rectifier section? Otherwise, the simplest, but most inelegant solution, is to buy an inverter for DC to house-voltage AC, then plug in the computer's transformer... James Cameron (cameronjames@snoc01.enet.dec.com)
dbell@cup.portal.com (David J Bell) (02/14/91)
>I'm interested in building a converter that would allow me to run a >Commodore VIC 20 computer from a 12v motorcycle battery. The >computer needs a 9v ac input. Is it possible to synthisize this >easily? The current load is less then 3 amps max. The setup will >be used in a robot. Anyone have any ideas? >John Nordlie University of North Dakota > Space Studies Dept. Probably very simple... The transformer originally used supplied feeds a rectifier and filter in the VIC-20. The drop across the diodes will probably drop the 12V DC to pretty close to the peak rectified voltage. The only possible problem I would anticipate is the chance that Commodore used the AC input to derive a negative supply. If this is the case, you would then have to open the case, determine the supplies required, and build a set of regulators to "split" the 12V into +/- 5 or whatever is required... Basically, you need to learn a little more about the VIC-20's power supply. Maybe some VIC hacker will post here? Dave
whit@milton.u.washington.edu (John Whitmore) (02/17/91)
In article <91043.135514UD186413@NDSUVM1.BITNET> UD186413@NDSUVM1.BITNET (Space Studies Student Organization) writes: >I'm interested in building a converter that would allow me to run a >Commodore VIC 20 computer from a 12v motorcycle battery. The >computer needs a 9v ac input. Is it possible to synthisize this >easily? The current load is less then 3 amps max. There were two slightly different VIC-20 designs; one used an external 5V/3A power supply and had 9VAC input only for some low-power internal uses (like the RF modulator). The earlier VIC-20's had only an external transformer, and only 9VAC input (2-pin power socket). If yours is the recent design (DIN multipin power plug), you can just regulate your +12V externally to +5, and try a '555 at 1 kHz with a moderate size coupling capacitor (20 to 50 uF) to make it AC for the 9VAC pin. It'll be marginal, but probably will work. If yours is the older design, consider taking out the old power transistor, and connecting a 5V regulator from the battery (or use a 6V battery and one diode to get it to about 5V). Again, a couple of places need the AC, but you can do that with a '555 (or do without; does a robot really need the TV output?) The VIC uses that 9VAC to generate +5 and some +12, but you'd have an easier time not trying to make AC; the VIC only needs it to get some DC power, so give it the DC and forget the AC. The 'VIC Programmer's Reference Manual' has a foldout schematic in the back, which will be well worth perusing. My copy is at home, or I'd be more specific. John Whitmore