Multiple small power supplies are always better than one big one. 4A would require more base current than the controlling circuitry can provide.
Calex power supply series#
There are many reasons why there is this limit but chief among them is that the series pass transistors require a controlling base current to drive them and the amount of base current is dependant on the current taken from the power supply. I reckon 1.5A should be the top limit of the Oakley PSU. Terjewinther wrote:Do you think it will be possible to get 4A out of it? These power up banks of modules one at a time reducing the initial current surge. If it is power on latch up, then one of those timed start up modules that Ken Stone does will do the trick. It's more sensitive on power up, hence the latch up. The thing is, the PSU's current limiting depends on the output voltage of the power supply. These need to be charged up at the moment of switch on and the only thing that restricts the current at this point is the resistance in the wiring, the internal resistance of the capacitor and the power supply's current limiting. Each module has a small 2.2uF capacitor on the power supply rail to ground. It's caused by the sudden surge in current when the modules are powered up. If the modular still powers up just fine you have a power latch up problem. Use a less fussy module like a Multimix or Fourmix and make sure the power plug goes in fast and correct. Try plugging in the last module into the Dizzy when the unit is powered up. 12 modules is a bit naff if it is though. Sounds like one rail is going down if the LEDs are lighting up.ĭoes sound like power on latch up. The best way to avoid this is to use a PSU that doesn't latch up on power up, but if you do come across it, then a timed power up system like the PCB project sold by CGS (Ken Stone) can help. It is caused by excessive start up currents taken by the modular. If you find occasionally that only one rail powers up this is latch up.
One other thing about the Calex and other Power One type power supplies - beware of latch up on power on. If you are happy with wiring mains power then replacing the PA-20 with a more substantial internal power transformer can be cost effective.īear in mind that the Calex also needs heatsinking or put somewhere where it can dissipate all that heat.
The limit is essentially set by the PA-20 and any heatsinking you have. The Oakley PSU will quite happily work with higher currents. This is the same as it is on the Oakley PSUs - I've just got two output pins connected together on the PCB. If you have Dizzies then simply take both ground wires back to the new power supply and join them onto the 0V output pin. The panel ground and module ground (pin 3 and 2 respectively on the Oakley power headers) should be connected together at the power supply. Catatemycaps wrote:Should I just connect the panel and 0V grounds as in MOTM?
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