PAL-1 power supply

[Magnus Olsson]

While I'm waiting for my kit to arrive (I realize that I may have to wait for quite some time due to the pandemic) I have a couple of questions:

1. Does the voltage regulator require a heatsink? I've seen some people mention that, but in most of the photos and videos that people have posted it seems to be without one. I realize that depends on what input voltage I'll be feeding it. 7 V power supplies don't seem very common..

2. I'm considering bypassing the voltage regulator and use 5V from a USB outlet instead. Is USB power "clean" enough for the purpose? I assume USB power from a computer comes from the computer's power supply and should be OK - is that right?

[Hans Otten]

7.5 V power supply is quite common and cheap from the chinese shops. A PAL-1 with a 7.5  V supply could run without a heat sink, with all expansions it becomes hot. 9V of course makes things worse.

USB power is fine. Be careful with polarity! Fatal error is .. fatal.

[Magnus Olsson]

Thanks for the answer. I'm a bit reluctant to order a power supply from China due to the uncertain delivery times at the moment - I wouldn't want it to turn up a month after the kit - so I'll either go for the 5V solution or try to get one locally.

How much current does a "bare" kit without expansions consume? I assume the 1 A rating is for an expanded system?

[Magnus Olsson]

If I may reply to myself, I see that Amazon have 7.5 V adapters in stock, but I might go for an adjustable-voltage one instead. The question is just how much current I need.

[GN L]

The basic kit without expansion consumes 0.43A at 7.5V through the L7805, if you want to bypass L7805, the basic kit consumes 0.416A at 5V.

> On Feb 14, 2022, at 6:11 AM, Magnus Olsson <mne...@gmail.com> wrote:
>
> If I may reply to myself, I see that Amazon have 7.5 V adapters in stock, but I might go for an adjustable-voltage one instead. The question is just how much current I need.
>
> On Sunday, February 13, 2022 at 11:06:08 PM UTC+1 Magnus Olsson wrote:
> Thanks for the answer. I'm a bit reluctant to order a power supply from China due to the uncertain delivery times at the moment - I wouldn't want it to turn up a month after the kit - so I'll either go for the 5V solution or try to get one locally.
>
> How much current does a "bare" kit without expansions consume? I assume the 1 A rating is for an expanded system?
>

Best,
Liu

[Hans Otten]

Adjustable may look handy, but again, a mistake is easily made. A dedicated 7.V 1A is error free. A heatsink on the 7805 is advisable anyway, it does not cost much and helps a lot to keep things cool.

[Magnus Olsson]

Thanks! 

On Monday, February 14, 2022 at 5:55:52 AM UTC+1 liuga...@gmail.com wrote:

[Magnus Olsson]

Now that I have a PAL-1 up and running I tried measuring the temperature of the regulator with an IR thermometer and it seems that with a 7.5 V power supply and just the basic kit, the regulator runs at about 50-60 degrees C without a heatsink. 

On Sunday, February 13, 2022 at 10:35:14 PM UTC+1 hansj...@gmail.com wrote:

[Hans Otten]

Good to hear the PAL-1 is up and running and the 7.5V keeps the regulator happy! Enjoy the fun!

[Neil Andretti]

[Jim McClanahan]

The switching regulators that replace the 7805 are fairly cheap these days. (Down to under $5 each.) I've been going to go through my Cromemco S100 and change out the regulators on the cards at some point, although I'm not sure that it isn't better just to bypass the regulator and use a 5 volt supply. I hate having that kind of heat on the board itself but I also worry about the failure mode of the switching regulators.

I do like having a meter to watch the current consumption and I have a nice vintage 5 volt metered supply that would match up nicely with it.

Thanks,

Jim

[Will Senn]

I'm a little confused by the power adapter requirement. What should I be looking for? I did a quick search for 7v 1a on amazon and a lot of options came up - none were 7v 1a, but there were 7v 2a  14 watt, and other models. I remember back in the day there being quite a variety of connectors, too...

Any chance there's a cheap, but workable adapter out there that somebody knows about and would like to share a link?

Thanks,

Will

[Magnus Olsson]

The current rating (1A vs 2A) is the maximum current it can supply, so having one rated at more than 1 A won't hurt.

I ended up buying this one:

Poppstar Universal Charger 3/4.5/5/6/7.5/9/12V 1.5A (1500mA) and 8 Interchangeable Connectors, LED, 150cm : Amazon.se: Electronics

There's a 1A version as well which is slightly cheaper. I set it to 7.5V and it works fine.