Russell McMahon

56,073 reputation

13190

bio	website	j.mp/NZPHOTOS
	location	Auckland, New Zealand
	age
visits	member for	2 years, 2 months
	seen	1 hour ago
stats	profile views	2,525

Electronic designer. Professional Engineer. Oldish aka "reasonably experienced" :-).
Contact - apptechnz gmail com <- you know the drill.

Special interest in technological solutions for developing country applications. Extensive in-China experience in product development & manufacturing in China.

Jack of all trades, Master of Electrical engineering. (aka ME (elec)) Interested in all aspects of modern technology. Professional qualifications in electrical engineering but practically proficient or conversant in many peripheral areas.

Recent extensive experience in solar powered LED lighting development and manufacturing in China for markets worldwide.

"Servant of the Most High God" / committed Christian. Happy to work enthusiastically and interact amicably with people of all nationalities and creeds.

Married with 2 adult children.

Obsessional photographer.

	56,073 reputation	bio	website	j.mp/NZPHOTOS	visits	member for	2 years, 2 months
13190 badges		location	Auckland, New Zealand		seen	1 hour ago

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1h	comment	How to fix a broken amp For "next time" - if the inverter is mains voltage out, as I understand it to be (eg 100 VAC 60 hZ) then using a 1:1 isolating transformer tends to " round things up" somewhat albeit rather informally. You need then to establish that the inverter does not mind driving the transformer.
1d	comment	Topology of solar PWM charger @ArikRaffaelFunke - ... For extra points they could use slow PWM to use it as a switch and fast PWM at 10 - 100 x as fast which is filtered by RC on the gate to provide DC control. \|\| Your very very great friend here would be an oscilloscope. \|\| For interest - where are you located?
1d	comment	Topology of solar PWM charger @ArikRaffaelFunke - Thanks for the addition - we are getting to the crux of the question :-). There is nothing majorly wrong with your thinking - it's more to do with the fine details of practice. Non ideal thinghs WILL be being done. How non ideal depends on the cleverness of the designers and how much they care. As noted in my 2nd addition above, while you say "PWM control" they could be running the switch in linear mode in some cases. Even if PWM is used this can be filtered to make the FET act as a resistor.
1d	revised	Topology of solar PWM charger added 3059 characters in body
1d	comment	Magnets and Hard drives Most HDDs are safe enough from the sensible use of magnets. It would take VERY strong magnetic fields to affect the media and strong varying fields to induce enough signal in circuitry. The latter effect can also affect SSDs but as long as you do not use you drive while in an MRI machine and as long as mice and other small biological samples are not levitating nearby odds are you are OK. Rubbing small (or large) rare earth magnets over the outer housing of an HDD may just possibly cause problems. Why you'd consider doing so is less certain.
1d	comment	DC/DC Converter minimum load? As well as what Dave et al say - be SURE SMPS moise is not affecting your meter. A simple filter can help when noise affects the meter. eg add 1k in series to voltmeter and say 100 uF across meter leads.
1d	comment	Topology of solar PWM charger Arik - see addition to my answer. Simple PWM of a FET will do what is claimed with a suitable controller.
1d	revised	Topology of solar PWM charger added 1792 characters in body
1d	revised	Topology of solar PWM charger added 415 characters in body
1d	answered	Topology of solar PWM charger
2d	comment	DIY kinetic energy harvester @mikeY - Essentially yes. Using a full wave bridge of Schottky diodes would probably be superior to get bidirectional action.
2d	revised	DIY kinetic energy harvester edited body
May 20	comment	1N5819 diode reading? 1N5819 diode is unusual in an iron transformer charger. You would usually find them in a switch mode charger. Yes? If they are short circuit in a SMPS charger it is not uncommon for there to also be other problems.
May 20	answered	1N5819 diode reading?
May 20	comment	DIY kinetic energy harvester Rex - see addition to my answer. For very small caps (100 pF - 10 NF) the meter will discharge them in time.
May 20	revised	DIY kinetic energy harvester added 923 characters in body
May 20	comment	DIY kinetic energy harvester @Rex did you look at the app notes. Some make it easy enough. BUT if you substitute a capacitor for the battery you ca get a good idea of what is happening. A common DMM (digital multimeter) a coil, a diode and a magnet and a say 10 megohm resistor across the capacitor when wanted, should be about enough, A small capacitor (100 pF t say 10 NF range) should charge with ease. As cap gets bigger charging may take multiple magnet swipes. Placing the resistor across the cap will discharge it in time. 10M and 1uF ceramic or Tantalum cap will discharge to ABOUT 60% in 10 seconds. Smaller caps faster.
May 18	comment	Switch transistor with a low voltage and current Going in right direction BUT Q1e shoud be ground returned and R5 in collector. As is base neds to be abve emoitter vy 2 x Vbe BUT hold uC cannot get there.
May 17	comment	Switch transistor with a low voltage and current General method is good. Having high side connectd floating processor is harder to deal with when off. Using hogh side MOSFET plus whatver else is neededmakes life easier.
May 17	comment	Switch transistor with a low voltage and current @pjc50 - ... Processor in sleep may crash and even microamps can destroy eg LiIon battery if battery is run flat and it is then put aside for months (can happen - depends on application).