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>> Home > Tags > circuit

Graupner Elke HF 408 by RNinMunich Fleet Admiral!   Posted: 3 days ago
BTW Allen, Dave's comments re 'old motors' go in the right direction but the basic thought and measurement technique are not quite right. There should never be ANY ohm meter reading between armature coils (i.e. motor supply connections) and case! Do by all means try this, but anything less than infinity, '---' on most digital meters, means a scrap motor😡 This test really requires an insulation test using what is commonly called a Mega meter. This has a crank generator which puts high voltage (ca 1000V+😲) across the unit under test. It measures the insulation resistance in millions of Ohms, hence the name Mega! For us modellers not a particularly useful or practical test! The most common form of deterioration in old motors is cracking and flaking of the insulating varnish of the armature windings. This does not normally cause shorts or spurious measurable resistance to the case but causes internal shorts in the windings thus reducing their resistance and therefore increasing the current they draw for a given voltage applied, as Dave indicated. There are two ways you can check this, if you have a decent Ohm meter, one less, one more accurate. The less accurate is done externally by measuring across the normal motor connections and thus include the resistance of the brushes and connections. Connect the meter where you normally connect the output from the ESC. Slowly rotate the motor so you can feel the slight 'click' as the motor moves from one winding to the next (or one magnetic pole to the next if you like😉) You should see a few Ohms resistance at each pole. Value depending on the quality of the carbon brushes. Better quality brushes (more copper content) = lower resistance. Note and compare each 'pole' reading. If one 'pole' reading is significantly lower than the others then that winding has an internal short😡 The motor may overheat in that winding, depending on how many wires are affected, and fail eventually. The more accurate method is to dismantle the motor and measure the winding resistances directly at the commutator, i.e. without the brushes in circuit. But this is only useful for nuts like me 😁 as in my 50 year old Taycol Target renovation. I was lucky no shorts and all windings same resistance + or - a gnat's whatsit!😊 Sooooo, to cut a long story sideways😉I think it's very unlikely your motor has any internal problems. I recently found one of the ancient Mabuchis I originally fitted in my HMS Hotspur destroyer 51 years ago, it still clattered along, bearings shot but electrically still OK 😊 Just take what you've got now down to the lake and give her a Go. If she looks right then she most probably is! As my German colleagues would say "Always a hand's width of water under your keel". Cheers Doug 😎 PS: "But trust me on the sunscreen" 😁

Graupner Elke HF 408 by RNinMunich Fleet Admiral!   Posted: 3 days ago
Veeery interestink!😉 I always thought that a motor's power rating referred to it's useful power output, not what it scoffs when it is stalled 🤔 Sure 40 x 7.2 = 288W but your full ahead current and watts measurement says the supply voltage was approx 6V. Interestingly some history research tells me that the Elke was originally intended for and supplied with a direct drive 280 motor. Graupner still lists it as such, albeit as 'Sold out' 🤔 Several German build blogs on the net confirm this, although others have also tried different motors, including Decaperms. Kit reviews (mostly on German sites) also mention that she was 'pretty quick' with the 280 motor. Can well imagine, I have 2 x 285s in my 107cm U-25 and she goes like a bat out of hell. 😉 Allen; your result of 40W + and 6.77Amps tells me the motor was running on roughly 6V. (40/6.77=5.91) If you really had a 7.2V pack connected it's got a duff cell (collapsing under load or short circuit) 😲 Carefully strip the pack, isolate the duff cell using a digital voltmeter, cut it out and send it to the great recycling nirvana! Then you have a powerful RX battery😉 Glad to hear you fitted the fuse👍 Leave the rest alone for now and sail her and see. I believe you will be more than happy with the performance and since the ESC is over dimensioned it should have no problems. Happy sailing, Doug 😎

Angela Mary by JRF1972 Chief Petty Officer   Posted: 11 days ago
Trawler enlarged to 1/48 from a free plan called Constant Star in a July 1966 Model boats 385 motor, 35mm 4 bladed brass prop, 6v battery, featuring sound unit and working lights on 3 circuits, Built from Scrap, about the Same Size as a billings Nordkap, but a lot Cheaper😊

happy hunter by RNinMunich Fleet Admiral!   Posted: 12 days ago
Careful with the MEK🤔 Ketones are dodgy, if you breathe the fumes at best it can give you a headache. Longer exposure is not good for the lungs and it sends glue sniffers round the twist. Use in well ventilated space! They are highly volatile (why it sets so fast!) and carcinogenic 😲 We used to use Methyl-ethyl-ketone many moons ago for cleaning circuit boards, I only had to be in the room with the stuff to get a migraine😡 Cheers Doug 😎

LiPo Battery Monitor by Dave M Fleet Admiral!   Posted: 22 days ago
Hi Bill Doug has shown a battery checker and alarm. You can get battery checkers see If you are going down the LiPo route I suggest you make sure the ESC you buy has a built in circuit which reduces the current should the battery volts drop below the set voltage (3.3v is common). In my experience the alarms although they work well are not loud enough to be heard, if your model is not near, and they do not cut or reduce the current, leaving your battery at risk of over discharging. Good luck with your model

rising damp by Dave M Fleet Admiral!   Posted: 26 days ago
Glad to hear the rx is working. All lake water contains salts and when an electrical circuit board gets wet the salts deposit on the tracks. Whilst drying often restores the Rx to a working state it may not be 100% due to residue as kmbc says above. I open the case and use Iso Propyl Alcohol and a stiff paint brush to clean any boards that have been exposed. This ensures the board is clean and reduces the chance of further failure. Another problem that might develop is the black wire syndrome so dismantling allows you to check the connection. I use WD 40 on the plug to drive out any water.

rising damp by kmbcsecretary Sub-Lieutenant   Posted: 26 days ago
Airing cupboard is best or if you have a cat use the cat litter. But the other problem you will have is the crystals left on the circuit board from the water will need to be cleaned of the circuit boards in the servos etc. Before you use them again or they will keep shorting out.

Brushless motors by Colin H. Fleet Admiral!   Posted: 1 month ago
Not thick at all, you only learn if you ask questions. ESC = Electronic Speed Control. BEC = Battery Eliminator Circuit. As to the rest I'm sure another member will put you right, try RNmunich he is well up on electrics. Cheers Colin.

MV TEAKWOOD by RHBaker Fleet Admiral!   Posted: 1 month ago
Before the funnel could be installed wanted to fit a working radar scanner, navigation lights and the batteries. Decided to use sub C NIMH batteries in plastic holders, they should have the target endurance and provide some ballast. Fitted two sets of 4 cells, one at the forward end of the superstructure and the other at the rear, both at keel level. These were inserted into wooden battery trays to hold them in place. A dry test run showed a full speed motor run time well exceeding the hour target, so will try on water. Also took the opportunity to fit the Rx and then adjust the rudder before finishing off the wiring. Both the navigation lights (LEDs) and the radar scanner work. The radar is driven by a servo with the potentiometer removed and a magnetic drive shaft run up through the superstructure from below the deck. The motor requires about 9 volts to run at what would seem to be something approximating to scale speed; fitted a voltage reducer to allow the lights and the radar to work on less than 6 volts. The mast lights are to be installed in a separate circuit after the masts are added. As I get more into the detail it is evident the GA drawing and the photographs of the vessel in service differ. Fortunately the component locations seem consistent, although the equipment is not. This most apparent in the hold ventilators. The GA shows the standard cowl vents, but the photographs show a mixture between an vertically squeezed oval vent (which am advised is more typically German) and ventilator columns with cylindrical caps. The column style vents with cylindrical caps were easily made from two different sizes of styrene tube with the cap tops made from styrene offcuts. The squeezed oval style vents were more difficult. Broke them down into the major parts of the cylindrical vertical tube and, from a larger tube cut a small ring and filed one end to straddle the tube once it had been squeezed oval. Glued it into place whilst restrained in a small hand vice. Once set, removed and sanded the the two to give a smooth transition, closing the rear aperture off with styrene offcuts. Then resorted to wood filler, filed down to give a smooth, oval vent.

Steam sound unit (variable speed) by Dave M Fleet Admiral!   Posted: 2 months ago
Doug Whilst I agree the sound systems you have found are excellent, am I right in thinking they are designed for the model truck market? I am sure they can be modified. There are circuits in Practical Electronics and I am just waiting for someone else to produce a working design smaller than a large mobile phone. The best steam sound unit I found for my tugs of the IMARA era came from Technobots, coupled to a 20Watt amp and 8" speaker. Sadly they no longer supply the sound unit, but there are other suppliers. If I recall one of our members was involved and I suggest you visit If you are using two ESCs you really need two units but one amp and speaker would be OK You did suggest similar using pre-amp mixer, which would allow mixing of other sounds. On my lake you can hear this system from the middle of the lake 50 yds+ so I have an on/off switch if it causes nuisance!?!

Water and Grease................ by NPJ Captain   Posted: 2 months ago
Thanks for that. I have picked up one or two references elsewhere that coating all connections made in wiring and servo connections is a good precaution. Also coating exposed circuit boards would benefit them. It is extremely unlikely that I would ever wish to make alterations to such boards, so if it does no harm and may be of benefit then I will have a go. You were right on the rudder links Mark. Better now that I have given them some 'slack' so will just use 3 in 1. All the best. NPJ

Water and Grease................ by jarvo Fleet Admiral!   Posted: 2 months ago
To be honest, I have never heard of the stuff, hence no comment!!! I will only advise if i have used the item or product. Do you think you will need that? Possibly WD40 would work just to dispel any moisture, If you spray sealed the circuit boards it might make it difficult to alter the wiring etc, only a thought as i said i have never used the product Mark

Water and Grease................ by NPJ Captain   Posted: 2 months ago
You can always rely upon Jarvo................ Thanks for that Mark. Will follow your guidance. Am I to read into the fact that you did not comment upon the attached as it was too 'way out' to consider? I was thinking of all connections having a spray and exposed circuit boards. All the best. NPJ

12v esc for trolling motor build by Dave M Fleet Admiral!   Posted: 2 months ago
Interesting project. Difficult to give advice on the info available. Looks like a steerable powered nozzle at the rear but what motor is it and what are the specs? An Esc does all the hard work and converts the rx pulses into usable power. I have arduinos and they can be programmed to control the power and rotation of a motor but would need additional high power Mosfets as well as other circuitry to buffer the unit from the output. If you are really into arduinos then a walk in the park but I believe an ESC would possibly be more robust and waterproof. It would be good if you were to post a build blog of your progress as the subject is certainly different to any models we have seen to-date. Good luck with the build

Power Cabling by NPJ Captain   Posted: 3 months ago
RN and others .............I have changed the fuse to 20 yellow for the battery and found it difficult! Are all the spade fuse holders as tight as mine? It took considerable force to remove the fuse from the holder and I wonder whether that is normal. I understand that looseness is not good but the force needed seems excessive and a threat to the circuit board etc. NPJ