Descrete designs VS "catalog engineering"

[zevon8]

Not sure if this is the right forum, but some coworkers and I debated this the other day and I thought maybe some members would have opinions on this also.

When you are designing something, do you generally prefer to build using descrete, generic components, or use some finished assemblies and products when it would be faster?

Say for example you need a controller that will operate a machine. Sure, you can develope the entire thing, microcontroller, software, power sections, etc, or you can use off the shelf parts for certain functions like power control, power supplies, etc.

Some times it doesn't pay to reinvent the wheel for certain things, but there are trade-offs. The costs can be higher, but you get simpler, field replaceable parts. Another issue is developement time...

Anyone have an opinion on this?

 

[Someone Electro]

We hobyists take the easyest and cheapest way of doing it.

I build evryting on a breadbord so i re use componnets there fore its not worth buying ICs and modules for spesific tasks.Rather find an schematic and make it my own.I dont often design stuff from scratch.I often modefy schematics or combine them to make what i want to do.

You have to think replacebility at parts that often wear out.These are mostly mechanical stuff like relays and switches electrolic capacitros wear out too.Then theres solid state stuff that is doing heavy duty stuff like handeling huge surge curent and voltage spikes.There are also stuff tahat burns out like LEDs,Lamps...

So you shod use module and off self stuff where it dosent wear out.For parts that do wear out use stuff that is easy to get.

 

[_3iMaJ]

Some times it doesn't pay to reinvent the wheel

Absolutely, I never reinvent the wheel. If someone built it first then I'll never go out of my way to complicate it.

 

[zevon8]

So you shod use module and off self stuff where it dosent wear out.For parts that do wear out use stuff that is easy to get.

That is one of the interesting parts of the debate...

Which is easier to get? A module from a big name manufacturer, replaced in 5 minutes, or an electrolytic capaitor that is cheaper, but will require skill/expertise to replace?

If it is something that may need replacing, is it easier/cheaper to swap a module, or get into board level repair? Board level repair can have the device out of service completely while repairs are being made. A module is more of a field replaceable unit that can be swapped with off the shelf parts.

 

[Someone Electro]

Yea but its easyer to find say an 100uF 16V cap than an module specialy designed for this device.

 

[Someone Electro]

Oh and if posible make it in litle boards that can be just pluged out to replace an faulty component and then pluged back in.(makes repair easyer)

 

[zevon8]

Yea but its easyer to find say an 100uF 16V cap than an module specialy designed for this device.

True, but the kind of modules I am refering to are more along the lines of say those digital I/O packs that mount on a DIN rail, or solid state relays, etc.

Oh and if posible make it in litle boards that can be just pluged out to replace an faulty component and then pluged back in.(makes repair easyer).

But that means I am the one making modules, LOL, just kidding

Also, if the device is located miles or continents away, somebody has to get them one of my circuit boards, instead of going to a supplier and buying a device made by Motorola or Weidmuller.

 

[samcheetah]

well, it all depends on the type of company you are working in. the managers decide where and how to put money in.

but in the field of telecom module level design is used. although you have to know the functionality at the component level but most of the time you just stick to the module level. if a modult gets bad then just replace it. nobody has the time to resolder one or two ICs.

i know a person who served in the army. his expertise was in missile guidance systems. he used to repair a specific type of guidance system and only he was the expert in it. he knew the whole thing upto the component level. then the company that used to make it stopped giving replacements for bad modules. at that time that person said that he would repair each and every board himself. that work gave him alot of $$$.

so you see its good that you should be able to design everything yourself. but it is easier to use a proven off the shelf product. that makes life easier. and thats what is done in all the industries.

 

[zevon8]

Good points samcheetah. One of the biggest problems we have at my work is when the customer uses the device incorrectly or does not follow the manual. We end up with alot of "needless" repairs that are not the fault of the device, but that it was mis-used, or incorrectly installed.

You could argue that if it is mis-used then the customer has to absorb the repair, and suffer the down time. However, today where economics dictates that it is often cheaper to replace than repair, sending a tech out in the field to component level repair is too expensive and time consuming. This is where the question of FRU ( feild replaceable units ) comes into the argument.

Add to this the fact that regardless of who is at fault, your product can get a "bad name" for failures, it seems to me quick repairs are favored.

An example of my work would be a $400,000 heavy truck that has some equipment on it that is prevented from doing its job because a $2 relay has failed. If I use a solid state relay module worth $50 but the customer can replace it, they will, glady, to get back on the road in an hour. I would have to send a tech to replace the $2 PCB mounted relay, and maybe not for a few days, depending where the vehicle is located.