{"id":16809,"date":"2021-07-09T22:20:08","date_gmt":"2021-07-10T02:20:08","guid":{"rendered":"https:\/\/scruss.com\/blog\/?p=16809"},"modified":"2022-05-16T20:02:03","modified_gmt":"2022-05-17T00:02:03","slug":"powering-a-cambridge-z88-with-a-mt3068-module","status":"publish","type":"post","link":"https:\/\/scruss.com\/blog\/2021\/07\/09\/powering-a-cambridge-z88-with-a-mt3068-module\/","title":{"rendered":"Powering a Cambridge Z88 with a MT3068 module"},"content":{"rendered":"\n
\"keyboard
my Z88 – USB power cable, with slightly stoory Z88 underneath<\/figcaption><\/figure>\n\n\n\n

I got a Cambridge Computer Z88<\/a> again, after perhaps 30 years of not having one. They are very nice little portable computers, remarkable for packing a multi-tasking OS into an 8-bit machine that runs for weeks on 4x AA batteries.<\/p>\n\n\n\n

But the Z88 is a Clive Sinclair joint, so there’s going to be at least one deeply weird and\/or ill-advised detail about it. For me, it’s the power adapter. The original had a 6 V centre-positive barrel connector, but in true Sinclair fashion, that wasn’t quite ideal.<\/p>\n\n\n\n

The DC power comes through a diode, which drops it down to ~5.2\u00a0V. The batteries supply up to 6\u00a0V and there’s no protection circuit, so the DC adapter won’t do anything until the internal batteries discharge down to that level. This is far from ideal.<\/p>\n\n\n\n

The clever way of dealing with this was Rakewell’s Z88 PSU<\/a>. This was a variable voltage PSU set to deliver 7\u00a0V, so that even when dropped through the power diode, it wouldn’t deplete the batteries.<\/p>\n\n\n\n

Unfortunately, Rakewell stopped selling these a while ago. But I remembered I had a some MT3608<\/a> (datasheet) boards bought at a hamfest some years back. MT3608s are boost DC-DC converters, so they’ll convert from a lower DC voltage to a higher one, typically at least +2\u00a0V higher than the input. With a hacked-up USB cable, a small length of DC cable with a connector and a 3d printed case, I built one that works quite well, at least in the short time I’ve tested it.<\/p>\n\n\n\n