quote for a job - Page 1
Forum section: electronics / projects

author: m3vuv
author_rank: Super Contributor
timestamp: June 24, 2019, 09:59:41 am
content: hi all,ive a schematic i need converting to a pcb layout for a job,i need the gerber files ready to send to have a boarrd made,can ppl who are interested give me a quote,can pay thru paypal,find attached schematic.,cheers m3vuv.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: June 24, 2019, 10:24:59 am
content: There are many informations missing to make a quote. Also, the schematic is a bit... odd. there are many open connections going to nowhere, what is that supposed to be?Please provide as many informations as possible.

author: strawberry
author_rank: Super Contributor
timestamp: June 24, 2019, 10:25:52 am
content: you could change CD4047 with PWM chip with built in soft start and inhibit and gate drive functions

author: sokoloff
author_rank: Super Contributor
timestamp: June 24, 2019, 10:35:02 am
content: Quote from: Ysjoelfir on June 24, 2019, 10:24:59 amMaybe some more context here:https://www.gotopcs.net/charger.htmIt seems like this is a "I have someone else's circuit that I want built" (which is totally fine; that's why the original guy presumably published it, but it does mean that you won't be able to easily get questions answered like "what the hell does this mean?!")I predict aggravations on both the buyer and designer side in this transaction, unfortunately.

author: m3vuv
author_rank: Super Contributor
timestamp: June 24, 2019, 11:27:17 am
content: Its for a control unit for a british rail railway carriage,the dynamo and field coil are on the vehicle.hope that helps.

author: tggzzz
author_rank: Super Contributor
timestamp: June 24, 2019, 11:50:57 am
content: Quote from: m3vuv on June 24, 2019, 11:27:17 amSo no standards have to be complied with, then.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 24, 2019, 12:23:18 pm
content: Quote from: tggzzz on June 24, 2019, 11:50:57 am

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: June 24, 2019, 12:51:43 pm
content: Quote from: m3vuv on June 24, 2019, 11:27:17 amWell... no.What kind of controlls do you want the pots and switches to be?What kind of transformer is that?Which relay do you need?Where the hell do those open wires go to?Which Connectors are apropriate for the application?Where is a connector for what needed?Space?Dimensions?Environment?Dirt and Water ingress protection levels?Shielding requirements?...

author: strawberry
author_rank: Super Contributor
timestamp: June 24, 2019, 01:10:20 pm
content: for 500Hz expect bulky steel transformer

author: dmills
author_rank: Super Contributor
timestamp: June 24, 2019, 04:57:38 pm
content: Stupid way to skin it.For all except the completely flat battery case you have a perfectly good source of 24V in the batteries themselves (Remember you only need a few amps for the field and once the field comes up the generator will pick up the load including its own field winding).All you need to do is detect when you have a vaguely reasonable shaft speed (say 12MPH or so) and then power the field from the battery directly (Relay or such), regulate field current to maintain setpoint, job done (Remember to protect the field switching device from back EMF when the contacts open!).Now if the batteries are fully flat then you need some sort of boost converter to run the field up to the point that it becomes self sustaining, but that should be very much the exceptional situation, and should probably be dealt with back at the shed by charging the batteries and putting a flea in the ear of whoever left the lights on overnight. You could even have a port to plug in a couple of 12V SLA cells to power the field if you had a really flat battery and needed to run the train right now, once the thing was in motion the generator would quickly bring the main battery up to voltage).I have actually seen video of the (modern diesel) Edinburgh sleeper needing one of its cars emergency batteries jumped from another car because the bus voltage was so low that the charging supplys would not turn on (Yep, someone had left the lights on with the carriage parked up).Hold on, sketching it...I think the controller is probably a TL494 or something of the sort (Or a small micro with a couple of ADCs, but that is harder to maintain long term, KISS very much applies).

author: MarkF
author_rank: Super Contributor
timestamp: June 24, 2019, 06:00:57 pm
content: Also, refer to his other thread on the same subject:https://www.eevblog.com/forum/projects/needing-some-help/

author: strawberry
author_rank: Super Contributor
timestamp: June 24, 2019, 06:19:04 pm
content: dmils There is no need for blocking diode when dinamo have built in rectifier. Field coil should be filtered rather than powered with PWM sq pulses.

author: dmills
author_rank: Super Contributor
timestamp: June 24, 2019, 06:42:03 pm
content: Field coil is an INDUCTOR, think about it, PWM with a catch diode, plus V=L.di/dt.You don't need to be burning power in a pass transistor, you can just run the field coil as the inductor in what is effectively a buck regulator, result little heat in the controller and if the switching frequency is reasonably high, largely constant field strength...Does the dynamo have a built in diode, or just a commutator?Most such have a commutator but that does not stop the thing from motoring if the speed is too low for the applied field strength.Regards, Dan.

author: m3vuv
author_rank: Super Contributor
timestamp: June 25, 2019, 04:23:51 am
content: no diodes in the dynamo just a commutator,the size doesent mater realy,also the relay im going to use is a 12v 30amp car relay as they are widley available,hope this helps for the conectors etc i just need big solder pads to fix some fly leads to.